`simplistic_calculator`: Breaking apart into a bunch of steps (#1033)

simplistic_calculator/analysis_options.yaml

@@ -1 +1,6 @@
 include: ../analysis_options.yaml
+
+# Files under typer/ are partially completed files, and often invalid
+analyzer:
+  exclude:
+    - typer/**

simplistic_calculator/lib/main.dart

@@ -12,9 +12,6 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:math_expressions/math_expressions.dart';
 import 'package:window_size/window_size.dart';
 
-const double windowWidth = 600;
-const double windowHeight = 900;
-
 void main() {
   if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
     WidgetsFlutterBinding.ensureInitialized();
@@ -472,7 +469,7 @@ class CalcButton extends ConsumerWidget {
 
     return SizedBox.expand(
       child: Padding(
-        padding: const EdgeInsets.all(8),
+        padding: const EdgeInsets.all(4),
         child: buttonConstructor(
           onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
           child: AutoSizeText(

simplistic_calculator/typer/main_01.dart

@@ -0,0 +1,33 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+
+void main() {
+  runApp(
+    const CalculatorApp(),
+  );
+}
+
+class CalculatorApp extends StatelessWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_02.dart

@@ -0,0 +1,37 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  runApp(
+    const CalculatorApp(),
+  );
+}
+
+class CalculatorApp extends StatelessWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_03.dart

@@ -0,0 +1,42 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const CalculatorApp(),
+  );
+}
+
+class CalculatorApp extends StatelessWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_04.dart

@@ -0,0 +1,43 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const CalculatorApp(),
+  );
+}
+
+class CalculatorApp extends StatelessWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_05.dart

@@ -0,0 +1,45 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+class CalculatorApp extends StatelessWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_06.dart

@@ -0,0 +1,48 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {}
+
+class CalculatorApp extends StatelessWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_07.dart

@@ -0,0 +1,50 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  final String buffer;
+}
+
+class CalculatorApp extends StatelessWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_08.dart

@@ -0,0 +1,51 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  final String buffer;
+  final String error;
+}
+
+class CalculatorApp extends StatelessWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_09.dart

@@ -0,0 +1,56 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    this.buffer,
+    this.error,
+  });
+
+  final String buffer;
+  final String error;
+}
+
+class CalculatorApp extends StatelessWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_10.dart

@@ -0,0 +1,56 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+}
+
+class CalculatorApp extends StatelessWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_11.dart

@@ -0,0 +1,65 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorApp extends StatelessWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_12.dart

@@ -0,0 +1,67 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {}
+
+class CalculatorApp extends StatelessWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_13.dart

@@ -0,0 +1,69 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine(CalculatorState state) : super(state);
+}
+
+class CalculatorApp extends StatelessWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_14.dart

@@ -0,0 +1,75 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+}
+
+class CalculatorApp extends StatelessWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_15.dart

@@ -0,0 +1,77 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {}
+}
+
+class CalculatorApp extends StatelessWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_16.dart

@@ -0,0 +1,82 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+class CalculatorApp extends StatelessWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_17.dart

@@ -0,0 +1,86 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends StatelessWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_18.dart

@@ -0,0 +1,86 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_19.dart

@@ -0,0 +1,86 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_20.dart

@@ -0,0 +1,88 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              'Hello GDSC!',
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_21.dart

@@ -0,0 +1,88 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: const Center(
+            child: Text(
+              state.buffer,
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_22.dart

@@ -0,0 +1,88 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: Center(
+            child: Text(
+              state.buffer,
+              style: TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_23.dart

@@ -0,0 +1,88 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: Center(
+            child: Text(
+              state.buffer,
+              style: const TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_24.dart

@@ -0,0 +1,89 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: Center(
+            child: Text(
+              state.buffer,
+              style: const TextStyle(fontSize: 40),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_25.dart

@@ -0,0 +1,91 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            children: [
+              Text(
+                state.buffer,
+                style: const TextStyle(fontSize: 40),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_26.dart

@@ -0,0 +1,93 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            columnSizes: [1.fr],
+            rowSizes: [1.fr],
+            children: [
+              Text(
+                state.buffer,
+                style: const TextStyle(fontSize: 40),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_27.dart

@@ -0,0 +1,106 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              Text(
+                state.buffer,
+                style: const TextStyle(fontSize: 40),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_28.dart

@@ -0,0 +1,109 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: Text(
+                  state.buffer,
+                  style: const TextStyle(fontSize: 40),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_29.dart

@@ -0,0 +1,110 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: Text(
+                  state.buffer,
+                  textAlign: TextAlign.end,
+                  style: const TextStyle(fontSize: 40),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_30.dart

@@ -0,0 +1,112 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 40),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_31.dart

@@ -0,0 +1,112 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 40),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_32.dart

@@ -0,0 +1,112 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_33.dart

@@ -0,0 +1,114 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+class CalcButton extends ConsumerWidget {}

simplistic_calculator/typer/main_34.dart

@@ -0,0 +1,120 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+class CalcButton extends ConsumerWidget {
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    // TODO: implement build
+    throw UnimplementedError();
+  }
+}

simplistic_calculator/typer/main_35.dart

@@ -0,0 +1,119 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+class CalcButton extends ConsumerWidget {
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton();
+  }
+}

simplistic_calculator/typer/main_36.dart

@@ -0,0 +1,121 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+class CalcButton extends ConsumerWidget {
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      child: null,
+    );
+  }
+}

simplistic_calculator/typer/main_37.dart

@@ -0,0 +1,122 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+class CalcButton extends ConsumerWidget {
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () {},
+      child: null,
+    );
+  }
+}

simplistic_calculator/typer/main_38.dart

@@ -0,0 +1,122 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+class CalcButton extends ConsumerWidget {
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () {},
+      child: Text(),
+    );
+  }
+}

simplistic_calculator/typer/main_39.dart

@@ -0,0 +1,124 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+class CalcButton extends ConsumerWidget {
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () {},
+      child: Text(),
+    );
+  }
+}

simplistic_calculator/typer/main_40.dart

@@ -0,0 +1,124 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+class CalcButton extends ConsumerWidget {
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () {},
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_41.dart

@@ -0,0 +1,129 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.label,
+  }) : super(key: key);
+
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () {},
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_42.dart

@@ -0,0 +1,131 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.label,
+  }) : super(key: key);
+
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () {},
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_43.dart

@@ -0,0 +1,132 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () {},
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_44.dart

@@ -0,0 +1,133 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_45.dart

@@ -0,0 +1,135 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {}
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_46.dart

@@ -0,0 +1,139 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_47.dart

@@ -0,0 +1,145 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_48.dart

@@ -0,0 +1,147 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_49.dart

@@ -0,0 +1,153 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_50.dart

@@ -0,0 +1,158 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_51.dart

@@ -0,0 +1,163 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_52.dart

@@ -0,0 +1,168 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_53.dart

@@ -0,0 +1,173 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_54.dart

@@ -0,0 +1,178 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_55.dart

@@ -0,0 +1,183 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_56.dart

@@ -0,0 +1,188 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_57.dart

@@ -0,0 +1,193 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_58.dart

@@ -0,0 +1,198 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_59.dart

@@ -0,0 +1,203 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_60.dart

@@ -0,0 +1,208 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_61.dart

@@ -0,0 +1,217 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return OutlinedButton(
+      onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+      child: Text(label),
+    );
+  }
+}

simplistic_calculator/typer/main_62.dart

@@ -0,0 +1,219 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return SizedBox(
+      child: OutlinedButton(
+        onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+        child: Text(label),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_63.dart

@@ -0,0 +1,219 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return SizedBox.expand(
+      child: OutlinedButton(
+        onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+        child: Text(label),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_64.dart

@@ -0,0 +1,222 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: OutlinedButton(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(label),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_65.dart

@@ -0,0 +1,225 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: OutlinedButton(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_66.dart

@@ -0,0 +1,226 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: OutlinedButton(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_67.dart

@@ -0,0 +1,227 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: OutlinedButton(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_68.dart

@@ -0,0 +1,228 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: OutlinedButton(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_69.dart

@@ -0,0 +1,232 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: OutlinedButton(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_70.dart

@@ -0,0 +1,232 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_71.dart

@@ -0,0 +1,233 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_72.dart

@@ -0,0 +1,234 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_73.dart

@@ -0,0 +1,235 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_74.dart

@@ -0,0 +1,236 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_75.dart

@@ -0,0 +1,238 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_76.dart

@@ -0,0 +1,239 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_77.dart

@@ -0,0 +1,240 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.mode,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_78.dart

@@ -0,0 +1,241 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.mode,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        mode: mode ?? this.mode,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_79.dart

@@ -0,0 +1,242 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.mode,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    CalculatorEngineMode? mode,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        mode: mode ?? this.mode,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_80.dart

@@ -0,0 +1,243 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.mode,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    CalculatorEngineMode? mode,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        mode: mode ?? this.mode,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            mode: CalculatorEngineMode.result,
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    state = state.copyWith(
+      buffer: state.buffer + str,
+      error: '',
+    );
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_81.dart

@@ -0,0 +1,251 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.mode,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    CalculatorEngineMode? mode,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        mode: mode ?? this.mode,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            mode: CalculatorEngineMode.result,
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    if (state.mode == CalculatorEngineMode.result) {
+      state = state.copyWith(
+        buffer: str,
+        mode: CalculatorEngineMode.input,
+        error: '',
+      );
+    } else {
+      state = state.copyWith(
+        buffer: state.buffer + str,
+        error: '',
+      );
+    }
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display
+              seven   eight   nine
+              four    five    six 
+              one     two     three
+              zero    point   equals
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_82.dart

@@ -0,0 +1,251 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.mode,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    CalculatorEngineMode? mode,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        mode: mode ?? this.mode,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            mode: CalculatorEngineMode.result,
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    if (state.mode == CalculatorEngineMode.result) {
+      state = state.copyWith(
+        buffer: str,
+        mode: CalculatorEngineMode.input,
+        error: '',
+      );
+    } else {
+      state = state.copyWith(
+        buffer: state.buffer + str,
+        error: '',
+      );
+    }
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display display
+              seven   eight   nine    divide
+              four    five    six     multiply
+              one     two     three   minus
+              zero    point   equals  plus
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_83.dart

@@ -0,0 +1,256 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.mode,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    CalculatorEngineMode? mode,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        mode: mode ?? this.mode,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            mode: CalculatorEngineMode.result,
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    if (state.mode == CalculatorEngineMode.result) {
+      state = state.copyWith(
+        buffer: str,
+        mode: CalculatorEngineMode.input,
+        error: '',
+      );
+    } else {
+      state = state.copyWith(
+        buffer: state.buffer + str,
+        error: '',
+      );
+    }
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+  ButtonDefinition(
+    areaName: 'plus',
+    op: (engine) => engine.addToBuffer('+'),
+    label: '+',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display display
+              seven   eight   nine    divide
+              four    five    six     multiply
+              one     two     three   minus
+              zero    point   equals  plus
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_84.dart

@@ -0,0 +1,261 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.mode,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    CalculatorEngineMode? mode,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        mode: mode ?? this.mode,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            mode: CalculatorEngineMode.result,
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    if (state.mode == CalculatorEngineMode.result) {
+      state = state.copyWith(
+        buffer: str,
+        mode: CalculatorEngineMode.input,
+        error: '',
+      );
+    } else {
+      state = state.copyWith(
+        buffer: state.buffer + str,
+        error: '',
+      );
+    }
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+  ButtonDefinition(
+    areaName: 'plus',
+    op: (engine) => engine.addToBuffer('+'),
+    label: '+',
+  ),
+  ButtonDefinition(
+    areaName: 'minus',
+    op: (engine) => engine.addToBuffer('-'),
+    label: '-',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display display
+              seven   eight   nine    divide
+              four    five    six     multiply
+              one     two     three   minus
+              zero    point   equals  plus
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_85.dart

@@ -0,0 +1,266 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.mode,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    CalculatorEngineMode? mode,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        mode: mode ?? this.mode,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            mode: CalculatorEngineMode.result,
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    if (state.mode == CalculatorEngineMode.result) {
+      state = state.copyWith(
+        buffer: str,
+        mode: CalculatorEngineMode.input,
+        error: '',
+      );
+    } else {
+      state = state.copyWith(
+        buffer: state.buffer + str,
+        error: '',
+      );
+    }
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+  ButtonDefinition(
+    areaName: 'plus',
+    op: (engine) => engine.addToBuffer('+'),
+    label: '+',
+  ),
+  ButtonDefinition(
+    areaName: 'minus',
+    op: (engine) => engine.addToBuffer('-'),
+    label: '-',
+  ),
+  ButtonDefinition(
+    areaName: 'multiply',
+    op: (engine) => engine.addToBuffer('*'),
+    label: '*',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display display
+              seven   eight   nine    divide
+              four    five    six     multiply
+              one     two     three   minus
+              zero    point   equals  plus
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_86.dart

@@ -0,0 +1,271 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.mode,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    CalculatorEngineMode? mode,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        mode: mode ?? this.mode,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            mode: CalculatorEngineMode.result,
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    if (state.mode == CalculatorEngineMode.result) {
+      state = state.copyWith(
+        buffer: str,
+        mode: CalculatorEngineMode.input,
+        error: '',
+      );
+    } else {
+      state = state.copyWith(
+        buffer: state.buffer + str,
+        error: '',
+      );
+    }
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+  ButtonDefinition(
+    areaName: 'plus',
+    op: (engine) => engine.addToBuffer('+'),
+    label: '+',
+  ),
+  ButtonDefinition(
+    areaName: 'minus',
+    op: (engine) => engine.addToBuffer('-'),
+    label: '-',
+  ),
+  ButtonDefinition(
+    areaName: 'multiply',
+    op: (engine) => engine.addToBuffer('*'),
+    label: '*',
+  ),
+  ButtonDefinition(
+    areaName: 'divide',
+    op: (engine) => engine.addToBuffer('/'),
+    label: '/',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display display
+              seven   eight   nine    divide
+              four    five    six     multiply
+              one     two     three   minus
+              zero    point   equals  plus
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_87.dart

@@ -0,0 +1,272 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:math_expressions/math_expressions.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.mode,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    CalculatorEngineMode? mode,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        mode: mode ?? this.mode,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            mode: CalculatorEngineMode.result,
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    if (state.mode == CalculatorEngineMode.result) {
+      state = state.copyWith(
+        buffer: str,
+        mode: CalculatorEngineMode.input,
+        error: '',
+      );
+    } else {
+      state = state.copyWith(
+        buffer: state.buffer + str,
+        error: '',
+      );
+    }
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+  ButtonDefinition(
+    areaName: 'plus',
+    op: (engine) => engine.addToBuffer('+'),
+    label: '+',
+  ),
+  ButtonDefinition(
+    areaName: 'minus',
+    op: (engine) => engine.addToBuffer('-'),
+    label: '-',
+  ),
+  ButtonDefinition(
+    areaName: 'multiply',
+    op: (engine) => engine.addToBuffer('*'),
+    label: '*',
+  ),
+  ButtonDefinition(
+    areaName: 'divide',
+    op: (engine) => engine.addToBuffer('/'),
+    label: '/',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display display
+              seven   eight   nine    divide
+              four    five    six     multiply
+              one     two     three   minus
+              zero    point   equals  plus
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_88.dart

@@ -0,0 +1,274 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:math_expressions/math_expressions.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.mode,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    CalculatorEngineMode? mode,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        mode: mode ?? this.mode,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            mode: CalculatorEngineMode.result,
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    if (state.mode == CalculatorEngineMode.result) {
+      state = state.copyWith(
+        buffer: str,
+        mode: CalculatorEngineMode.input,
+        error: '',
+      );
+    } else {
+      state = state.copyWith(
+        buffer: state.buffer + str,
+        error: '',
+      );
+    }
+  }
+
+  void evaluate() {}
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+  ButtonDefinition(
+    areaName: 'plus',
+    op: (engine) => engine.addToBuffer('+'),
+    label: '+',
+  ),
+  ButtonDefinition(
+    areaName: 'minus',
+    op: (engine) => engine.addToBuffer('-'),
+    label: '-',
+  ),
+  ButtonDefinition(
+    areaName: 'multiply',
+    op: (engine) => engine.addToBuffer('*'),
+    label: '*',
+  ),
+  ButtonDefinition(
+    areaName: 'divide',
+    op: (engine) => engine.addToBuffer('/'),
+    label: '/',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display display
+              seven   eight   nine    divide
+              four    five    six     multiply
+              one     two     three   minus
+              zero    point   equals  plus
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_89.dart

@@ -0,0 +1,282 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:math_expressions/math_expressions.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.mode,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    CalculatorEngineMode? mode,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        mode: mode ?? this.mode,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            mode: CalculatorEngineMode.result,
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    if (state.mode == CalculatorEngineMode.result) {
+      state = state.copyWith(
+        buffer: str,
+        mode: CalculatorEngineMode.input,
+        error: '',
+      );
+    } else {
+      state = state.copyWith(
+        buffer: state.buffer + str,
+        error: '',
+      );
+    }
+  }
+
+  void evaluate() {
+    try {} catch (err) {
+      state = state.copyWith(
+        error: err.toString(),
+        buffer: '',
+        mode: CalculatorEngineMode.result,
+      );
+    }
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+  ButtonDefinition(
+    areaName: 'plus',
+    op: (engine) => engine.addToBuffer('+'),
+    label: '+',
+  ),
+  ButtonDefinition(
+    areaName: 'minus',
+    op: (engine) => engine.addToBuffer('-'),
+    label: '-',
+  ),
+  ButtonDefinition(
+    areaName: 'multiply',
+    op: (engine) => engine.addToBuffer('*'),
+    label: '*',
+  ),
+  ButtonDefinition(
+    areaName: 'divide',
+    op: (engine) => engine.addToBuffer('/'),
+    label: '/',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display display
+              seven   eight   nine    divide
+              four    five    six     multiply
+              one     two     three   minus
+              zero    point   equals  plus
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_90.dart

@@ -0,0 +1,287 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:math_expressions/math_expressions.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.mode,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    CalculatorEngineMode? mode,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        mode: mode ?? this.mode,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            mode: CalculatorEngineMode.result,
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    if (state.mode == CalculatorEngineMode.result) {
+      state = state.copyWith(
+        buffer: str,
+        mode: CalculatorEngineMode.input,
+        error: '',
+      );
+    } else {
+      state = state.copyWith(
+        buffer: state.buffer + str,
+        error: '',
+      );
+    }
+  }
+
+  void evaluate() {
+    try {
+      final parser = Parser();
+      final cm = ContextModel();
+      final exp = parser.parse(state.buffer);
+      final result = exp.evaluate(EvaluationType.REAL, cm) as double;
+    } catch (err) {
+      state = state.copyWith(
+        error: err.toString(),
+        buffer: '',
+        mode: CalculatorEngineMode.result,
+      );
+    }
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+  ButtonDefinition(
+    areaName: 'plus',
+    op: (engine) => engine.addToBuffer('+'),
+    label: '+',
+  ),
+  ButtonDefinition(
+    areaName: 'minus',
+    op: (engine) => engine.addToBuffer('-'),
+    label: '-',
+  ),
+  ButtonDefinition(
+    areaName: 'multiply',
+    op: (engine) => engine.addToBuffer('*'),
+    label: '*',
+  ),
+  ButtonDefinition(
+    areaName: 'divide',
+    op: (engine) => engine.addToBuffer('/'),
+    label: '/',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display display
+              seven   eight   nine    divide
+              four    five    six     multiply
+              one     two     three   minus
+              zero    point   equals  plus
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_91.dart

@@ -0,0 +1,300 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:math_expressions/math_expressions.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.mode,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    CalculatorEngineMode? mode,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        mode: mode ?? this.mode,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            mode: CalculatorEngineMode.result,
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    if (state.mode == CalculatorEngineMode.result) {
+      state = state.copyWith(
+        buffer: str,
+        mode: CalculatorEngineMode.input,
+        error: '',
+      );
+    } else {
+      state = state.copyWith(
+        buffer: state.buffer + str,
+        error: '',
+      );
+    }
+  }
+
+  void evaluate() {
+    try {
+      final parser = Parser();
+      final cm = ContextModel();
+      final exp = parser.parse(state.buffer);
+      final result = exp.evaluate(EvaluationType.REAL, cm) as double;
+
+      if (result.isInfinite) {
+        state = state.copyWith(
+          error: 'Result is Infinite',
+          buffer: '',
+          mode: CalculatorEngineMode.result,
+        );
+      } else if (result.isNaN) {
+        state = state.copyWith(
+          error: 'Result is Not a Number',
+          buffer: '',
+          mode: CalculatorEngineMode.result,
+        );
+    } catch (err) {
+      state = state.copyWith(
+        error: err.toString(),
+        buffer: '',
+        mode: CalculatorEngineMode.result,
+      );
+    }
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+  ButtonDefinition(
+    areaName: 'plus',
+    op: (engine) => engine.addToBuffer('+'),
+    label: '+',
+  ),
+  ButtonDefinition(
+    areaName: 'minus',
+    op: (engine) => engine.addToBuffer('-'),
+    label: '-',
+  ),
+  ButtonDefinition(
+    areaName: 'multiply',
+    op: (engine) => engine.addToBuffer('*'),
+    label: '*',
+  ),
+  ButtonDefinition(
+    areaName: 'divide',
+    op: (engine) => engine.addToBuffer('/'),
+    label: '/',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display display
+              seven   eight   nine    divide
+              four    five    six     multiply
+              one     two     three   minus
+              zero    point   equals  plus
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_92.dart

@@ -0,0 +1,309 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:math_expressions/math_expressions.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.mode,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    CalculatorEngineMode? mode,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        mode: mode ?? this.mode,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            mode: CalculatorEngineMode.result,
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    if (state.mode == CalculatorEngineMode.result) {
+      state = state.copyWith(
+        buffer: str,
+        mode: CalculatorEngineMode.input,
+        error: '',
+      );
+    } else {
+      state = state.copyWith(
+        buffer: state.buffer + str,
+        error: '',
+      );
+    }
+  }
+
+  void evaluate() {
+    try {
+      final parser = Parser();
+      final cm = ContextModel();
+      final exp = parser.parse(state.buffer);
+      final result = exp.evaluate(EvaluationType.REAL, cm) as double;
+
+      if (result.isInfinite) {
+        state = state.copyWith(
+          error: 'Result is Infinite',
+          buffer: '',
+          mode: CalculatorEngineMode.result,
+        );
+      } else if (result.isNaN) {
+        state = state.copyWith(
+          error: 'Result is Not a Number',
+          buffer: '',
+          mode: CalculatorEngineMode.result,
+        );
+      } else {
+        final resultStr = result.ceil() == result
+            ? result.toInt().toString()
+            : result.toString();
+        state = state.copyWith(
+          buffer: resultStr,
+          mode: CalculatorEngineMode.result,
+        );
+      }
+    } catch (err) {
+      state = state.copyWith(
+        error: err.toString(),
+        buffer: '',
+        mode: CalculatorEngineMode.result,
+      );
+    }
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) {},
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+  ButtonDefinition(
+    areaName: 'plus',
+    op: (engine) => engine.addToBuffer('+'),
+    label: '+',
+  ),
+  ButtonDefinition(
+    areaName: 'minus',
+    op: (engine) => engine.addToBuffer('-'),
+    label: '-',
+  ),
+  ButtonDefinition(
+    areaName: 'multiply',
+    op: (engine) => engine.addToBuffer('*'),
+    label: '*',
+  ),
+  ButtonDefinition(
+    areaName: 'divide',
+    op: (engine) => engine.addToBuffer('/'),
+    label: '/',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display display
+              seven   eight   nine    divide
+              four    five    six     multiply
+              one     two     three   minus
+              zero    point   equals  plus
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_93.dart

@@ -0,0 +1,309 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:math_expressions/math_expressions.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.mode,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    CalculatorEngineMode? mode,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        mode: mode ?? this.mode,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            mode: CalculatorEngineMode.result,
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    if (state.mode == CalculatorEngineMode.result) {
+      state = state.copyWith(
+        buffer: str,
+        mode: CalculatorEngineMode.input,
+        error: '',
+      );
+    } else {
+      state = state.copyWith(
+        buffer: state.buffer + str,
+        error: '',
+      );
+    }
+  }
+
+  void evaluate() {
+    try {
+      final parser = Parser();
+      final cm = ContextModel();
+      final exp = parser.parse(state.buffer);
+      final result = exp.evaluate(EvaluationType.REAL, cm) as double;
+
+      if (result.isInfinite) {
+        state = state.copyWith(
+          error: 'Result is Infinite',
+          buffer: '',
+          mode: CalculatorEngineMode.result,
+        );
+      } else if (result.isNaN) {
+        state = state.copyWith(
+          error: 'Result is Not a Number',
+          buffer: '',
+          mode: CalculatorEngineMode.result,
+        );
+      } else {
+        final resultStr = result.ceil() == result
+            ? result.toInt().toString()
+            : result.toString();
+        state = state.copyWith(
+          buffer: resultStr,
+          mode: CalculatorEngineMode.result,
+        );
+      }
+    } catch (err) {
+      state = state.copyWith(
+        error: err.toString(),
+        buffer: '',
+        mode: CalculatorEngineMode.result,
+      );
+    }
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) => engine.evaluate(),
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+  ButtonDefinition(
+    areaName: 'plus',
+    op: (engine) => engine.addToBuffer('+'),
+    label: '+',
+  ),
+  ButtonDefinition(
+    areaName: 'minus',
+    op: (engine) => engine.addToBuffer('-'),
+    label: '-',
+  ),
+  ButtonDefinition(
+    areaName: 'multiply',
+    op: (engine) => engine.addToBuffer('*'),
+    label: '*',
+  ),
+  ButtonDefinition(
+    areaName: 'divide',
+    op: (engine) => engine.addToBuffer('/'),
+    label: '/',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display display
+              seven   eight   nine    divide
+              four    five    six     multiply
+              one     two     three   minus
+              zero    point   equals  plus
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: Text(
+                    state.buffer,
+                    textAlign: TextAlign.end,
+                    style: const TextStyle(fontSize: 80),
+                  ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/main_94.dart

@@ -0,0 +1,319 @@
+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_layout_grid/flutter_layout_grid.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:math_expressions/math_expressions.dart';
+import 'package:window_size/window_size.dart';
+
+void main() {
+  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+    WidgetsFlutterBinding.ensureInitialized();
+    setWindowTitle('Simplistic Calculator');
+  }
+
+  runApp(
+    const ProviderScope(
+      child: CalculatorApp(),
+    ),
+  );
+}
+
+@immutable
+class CalculatorState {
+  const CalculatorState({
+    required this.buffer,
+    required this.mode,
+    required this.error,
+  });
+
+  final String buffer;
+  final CalculatorEngineMode mode;
+  final String error;
+
+  CalculatorState copyWith({
+    String? buffer,
+    CalculatorEngineMode? mode,
+    String? error,
+  }) =>
+      CalculatorState(
+        buffer: buffer ?? this.buffer,
+        mode: mode ?? this.mode,
+        error: error ?? this.error,
+      );
+}
+
+enum CalculatorEngineMode { input, result }
+
+class CalculatorEngine extends StateNotifier<CalculatorState> {
+  CalculatorEngine()
+      : super(
+          const CalculatorState(
+            buffer: '0',
+            mode: CalculatorEngineMode.result,
+            error: '',
+          ),
+        );
+
+  void addToBuffer(String str) {
+    if (state.mode == CalculatorEngineMode.result) {
+      state = state.copyWith(
+        buffer: str,
+        mode: CalculatorEngineMode.input,
+        error: '',
+      );
+    } else {
+      state = state.copyWith(
+        buffer: state.buffer + str,
+        error: '',
+      );
+    }
+  }
+
+  void evaluate() {
+    try {
+      final parser = Parser();
+      final cm = ContextModel();
+      final exp = parser.parse(state.buffer);
+      final result = exp.evaluate(EvaluationType.REAL, cm) as double;
+
+      if (result.isInfinite) {
+        state = state.copyWith(
+          error: 'Result is Infinite',
+          buffer: '',
+          mode: CalculatorEngineMode.result,
+        );
+      } else if (result.isNaN) {
+        state = state.copyWith(
+          error: 'Result is Not a Number',
+          buffer: '',
+          mode: CalculatorEngineMode.result,
+        );
+      } else {
+        final resultStr = result.ceil() == result
+            ? result.toInt().toString()
+            : result.toString();
+        state = state.copyWith(
+          buffer: resultStr,
+          mode: CalculatorEngineMode.result,
+        );
+      }
+    } catch (err) {
+      state = state.copyWith(
+        error: err.toString(),
+        buffer: '',
+        mode: CalculatorEngineMode.result,
+      );
+    }
+  }
+}
+
+final calculatorStateProvider =
+    StateNotifierProvider<CalculatorEngine, CalculatorState>(
+        (_) => CalculatorEngine());
+
+class ButtonDefinition {
+  const ButtonDefinition({
+    required this.areaName,
+    required this.label,
+    required this.op,
+    this.type = CalcButtonType.outlined,
+  });
+
+  final String areaName;
+  final String label;
+  final CalculatorEngineCallback op;
+  final CalcButtonType type;
+}
+
+final buttonDefinitions = <ButtonDefinition>[
+  ButtonDefinition(
+    areaName: 'seven',
+    op: (engine) => engine.addToBuffer('7'),
+    label: '7',
+  ),
+  ButtonDefinition(
+    areaName: 'eight',
+    op: (engine) => engine.addToBuffer('8'),
+    label: '8',
+  ),
+  ButtonDefinition(
+    areaName: 'nine',
+    op: (engine) => engine.addToBuffer('9'),
+    label: '9',
+  ),
+  ButtonDefinition(
+    areaName: 'four',
+    op: (engine) => engine.addToBuffer('4'),
+    label: '4',
+  ),
+  ButtonDefinition(
+    areaName: 'five',
+    op: (engine) => engine.addToBuffer('5'),
+    label: '5',
+  ),
+  ButtonDefinition(
+    areaName: 'six',
+    op: (engine) => engine.addToBuffer('6'),
+    label: '6',
+  ),
+  ButtonDefinition(
+    areaName: 'one',
+    op: (engine) => engine.addToBuffer('1'),
+    label: '1',
+  ),
+  ButtonDefinition(
+    areaName: 'two',
+    op: (engine) => engine.addToBuffer('2'),
+    label: '2',
+  ),
+  ButtonDefinition(
+    areaName: 'three',
+    op: (engine) => engine.addToBuffer('3'),
+    label: '3',
+  ),
+  ButtonDefinition(
+    areaName: 'zero',
+    op: (engine) => engine.addToBuffer('0'),
+    label: '0',
+  ),
+  ButtonDefinition(
+    areaName: 'point',
+    op: (engine) => engine.addToBuffer('.'),
+    label: '.',
+  ),
+  ButtonDefinition(
+    areaName: 'equals',
+    op: (engine) => engine.evaluate(),
+    label: '=',
+    type: CalcButtonType.elevated,
+  ),
+  ButtonDefinition(
+    areaName: 'plus',
+    op: (engine) => engine.addToBuffer('+'),
+    label: '+',
+  ),
+  ButtonDefinition(
+    areaName: 'minus',
+    op: (engine) => engine.addToBuffer('-'),
+    label: '-',
+  ),
+  ButtonDefinition(
+    areaName: 'multiply',
+    op: (engine) => engine.addToBuffer('*'),
+    label: '*',
+  ),
+  ButtonDefinition(
+    areaName: 'divide',
+    op: (engine) => engine.addToBuffer('/'),
+    label: '/',
+  ),
+];
+
+class CalculatorApp extends ConsumerWidget {
+  const CalculatorApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final state = ref.watch(calculatorStateProvider);
+
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: Container(
+          color: Colors.white,
+          child: LayoutGrid(
+            areas: '''
+              display display display display
+              seven   eight   nine    divide
+              four    five    six     multiply
+              one     two     three   minus
+              zero    point   equals  plus
+              ''',
+            columnSizes: [1.fr, 1.fr, 1.fr, 1.fr],
+            rowSizes: [
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+              1.fr,
+            ],
+            children: [
+              NamedAreaGridPlacement(
+                areaName: 'display',
+                child: SizedBox.expand(
+                  child: state.error.isEmpty
+                      ? Text(
+                          state.buffer,
+                          textAlign: TextAlign.end,
+                          style: const TextStyle(fontSize: 80),
+                        )
+                      : Text(
+                          state.error,
+                          textAlign: TextAlign.start,
+                          style: const TextStyle(
+                            fontSize: 40,
+                            color: Colors.red,
+                          ),
+                          maxLines: 2,
+                        ),
+                ),
+              ),
+              ...buttonDefinitions.map(
+                (definition) => NamedAreaGridPlacement(
+                  areaName: definition.areaName,
+                  child: CalcButton(
+                    label: definition.label,
+                    op: definition.op,
+                    type: definition.type,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+typedef CalculatorEngineCallback = void Function(CalculatorEngine engine);
+enum CalcButtonType { outlined, elevated }
+
+class CalcButton extends ConsumerWidget {
+  const CalcButton({
+    Key? key,
+    required this.op,
+    required this.label,
+    required this.type,
+  }) : super(key: key);
+
+  final CalculatorEngineCallback op;
+  final String label;
+  final CalcButtonType type;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final buttonConstructor = type == CalcButtonType.elevated
+        ? ElevatedButton.new
+        : OutlinedButton.new;
+
+    return SizedBox.expand(
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: buttonConstructor(
+          onPressed: () => op(ref.read(calculatorStateProvider.notifier)),
+          child: Text(
+            label,
+            style: const TextStyle(fontSize: 40, color: Colors.black54),
+          ),
+        ),
+      ),
+    );
+  }
+}

simplistic_calculator/typer/steps.json

@@ -0,0 +1,378 @@
+[
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_01.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_02.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_03.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_04.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_05.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_06.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_07.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_08.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_09.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_10.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_11.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_12.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_13.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_14.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_15.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_16.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_17.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_18.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_19.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_20.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_21.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_22.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_23.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_24.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_25.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_26.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_27.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_28.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_29.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_30.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_31.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_32.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_33.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_34.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_35.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_36.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_37.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_38.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_39.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_40.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_41.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_42.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_43.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_44.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_45.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_46.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_47.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_48.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_49.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_50.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_51.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_52.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_53.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_54.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_55.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_56.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_57.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_58.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_59.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_60.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_61.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_62.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_63.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_64.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_65.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_66.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_67.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_68.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_69.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_70.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_71.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_72.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_73.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_74.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_75.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_76.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_77.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_78.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_79.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_80.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_81.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_82.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_83.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_84.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_85.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_86.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_87.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_88.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_89.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_90.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_91.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_92.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_93.dart"
+    },
+    {
+        "file":"lib/main.dart",
+        "content":"typer/main_94.dart"
+    }
+]