feat: gravity override (#192)

lib/game/components/score_effect_controller.dart

@@ -37,7 +37,7 @@ class ScoreEffectController extends ComponentController<PinballGame>
         text: newScore.toString(),
         position: Vector2(
           _noise(),
-          _noise() + (-BoardDimensions.bounds.topCenter.dy + 10),
+          _noise() + (BoardDimensions.bounds.topCenter.dy + 10),
         ),
       ),
     );

packages/pinball_components/lib/src/components/ball.dart

@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'dart:math' as math;
 import 'dart:ui';
 
 import 'package:flame/components.dart';
@@ -107,7 +108,8 @@ class Ball<T extends Forge2DGame> extends BodyComponent<T>
       unawaited(gameRef.add(effect));
     }
 
-    _rescale();
+    _rescaleSize();
+    _setPositionalGravity();
   }
 
   /// Applies a boost on this [Ball].
@@ -116,19 +118,36 @@ class Ball<T extends Forge2DGame> extends BodyComponent<T>
     _boostTimer = _boostDuration;
   }
 
-  void _rescale() {
+  void _rescaleSize() {
     final boardHeight = BoardDimensions.bounds.height;
-    const maxShrinkAmount = BoardDimensions.perspectiveShrinkFactor;
+    const maxShrinkValue = BoardDimensions.perspectiveShrinkFactor;
 
-    final adjustedYPosition = -body.position.y + (boardHeight / 2);
+    final standardizedYPosition = body.position.y + (boardHeight / 2);
 
-    final scaleFactor = ((boardHeight - adjustedYPosition) /
-            BoardDimensions.shrinkAdjustedHeight) +
-        maxShrinkAmount;
+    final scaleFactor = maxShrinkValue +
+        ((standardizedYPosition / boardHeight) * (1 - maxShrinkValue));
 
     body.fixtures.first.shape.radius = (size.x / 2) * scaleFactor;
     _spriteComponent.scale = Vector2.all(scaleFactor);
   }
+
+  void _setPositionalGravity() {
+    final defaultGravity = gameRef.world.gravity.y;
+    final maxXDeviationFromCenter = BoardDimensions.bounds.width / 2;
+    const maxXGravityPercentage =
+        (1 - BoardDimensions.perspectiveShrinkFactor) / 2;
+    final xDeviationFromCenter = body.position.x;
+
+    final positionalXForce = ((xDeviationFromCenter / maxXDeviationFromCenter) *
+            maxXGravityPercentage) *
+        defaultGravity;
+
+    final positionalYForce = math.sqrt(
+      math.pow(defaultGravity, 2) - math.pow(positionalXForce, 2),
+    );
+
+    body.gravityOverride = Vector2(positionalXForce, positionalYForce);
+  }
 }
 
 class _BallSpriteComponent extends SpriteComponent with HasGameRef {

packages/pinball_components/lib/src/components/board_dimensions.dart

@@ -22,8 +22,4 @@ class BoardDimensions {
 
   /// Factor the board shrinks by from the closest point to the farthest.
   static const perspectiveShrinkFactor = 0.63;
-
-  /// Board height based on the [perspectiveShrinkFactor].
-  static final shrinkAdjustedHeight =
-      (1 / (1 - perspectiveShrinkFactor)) * size.y;
 }

packages/pinball_components/test/src/components/board_dimensions_test.dart

@@ -19,9 +19,5 @@ void main() {
     test('has perspectiveShrinkFactor', () {
       expect(BoardDimensions.perspectiveShrinkFactor, equals(0.63));
     });
-
-    test('has shrinkAdjustedHeight', () {
-      expect(BoardDimensions.shrinkAdjustedHeight, isNotNull);
-    });
   });
 }