feat: made SlingShot rounded

lib/game/components/sling_shot.dart

@@ -1,7 +1,9 @@
+import 'dart:math' as math;
+
 import 'package:flame/extensions.dart';
 import 'package:flame_forge2d/flame_forge2d.dart';
 import 'package:flutter/material.dart';
-import 'package:geometry/geometry.dart' show centroid;
+import 'package:geometry/geometry.dart' as geometry show centroid;
 import 'package:pinball/game/game.dart';
 
 /// {@template sling_shot}
@@ -31,54 +33,94 @@ class SlingShot extends BodyComponent with InitialPosition {
   /// The size of the [SlingShot] body.
   // TODO(alestiago): Use size from PositionedBodyComponent instead,
   // once a sprite is given.
-  static final Vector2 size = Vector2(6, 8);
+  static final Vector2 size = Vector2(4, 10);
 
   List<FixtureDef> _createFixtureDefs() {
-    final fixturesDef = <FixtureDef>[];
+    final fixturesDefs = <FixtureDef>[];
+    final direction = _side.direction;
+    const quarterPi = math.pi / 4;
 
-    // TODO(alestiago): This magic number can be deduced by specifying the
-    // angle and using polar coordinate system to place the bottom right
-    // vertex.
-    // Something as: y = -size.y * math.cos(angle)
-    const additionalIncrement = 3;
-    final triangleVertices = _side.isLeft
-        ? [
-            Vector2(0, 0),
-            Vector2(0, -size.y),
-            Vector2(
-              size.x,
-              -size.y - additionalIncrement,
-            ),
-          ]
-        : [
-            Vector2(size.x, 0),
-            Vector2(size.x, -size.y),
+    final upperCircle = CircleShape()..radius = 1.45;
+    upperCircle.position.setValues(0, -upperCircle.radius / 2);
+    final upperCircleFixtureDef = FixtureDef(upperCircle);
+    fixturesDefs.add(upperCircleFixtureDef);
+
+    final lowerCircle = CircleShape()..radius = 1.45;
+    lowerCircle.position.setValues(
+      size.x * -direction,
+      -size.y,
+    );
+    final lowerCircleFixtureDef = FixtureDef(lowerCircle);
+    fixturesDefs.add(lowerCircleFixtureDef);
+
+    final wallFacingEdge = EdgeShape()
+      ..set(
+        upperCircle.position +
             Vector2(
+              upperCircle.radius * direction,
               0,
-              -size.y - additionalIncrement,
             ),
-          ];
-    final triangleCentroid = centroid(triangleVertices);
-    for (final vertex in triangleVertices) {
-      vertex.setFrom(vertex - triangleCentroid);
-    }
+        // TODO(alestiago): Use values from design.
+        Vector2(2.0 * direction, -size.y + 2),
+      );
+    final wallFacingLineFixtureDef = FixtureDef(wallFacingEdge);
+    fixturesDefs.add(wallFacingLineFixtureDef);
 
-    final triangle = PolygonShape()..set(triangleVertices);
-    final triangleFixtureDef = FixtureDef(triangle)..friction = 0;
-    fixturesDef.add(triangleFixtureDef);
+    final bottomEdge = EdgeShape()
+      ..set(
+        wallFacingEdge.vertex2,
+        lowerCircle.position +
+            Vector2(
+              lowerCircle.radius * math.cos(quarterPi) * direction,
+              -lowerCircle.radius * math.sin(quarterPi),
+            ),
+      );
+    final bottomLineFixtureDef = FixtureDef(bottomEdge);
+    fixturesDefs.add(bottomLineFixtureDef);
 
-    final kicker = EdgeShape()
+    final kickerEdge = EdgeShape()
       ..set(
-        triangleVertices.first,
-        triangleVertices.last,
+        upperCircle.position +
+            Vector2(
+              upperCircle.radius * math.cos(quarterPi) * -direction,
+              upperCircle.radius * math.sin(quarterPi),
+            ),
+        lowerCircle.position +
+            Vector2(
+              lowerCircle.radius * math.cos(quarterPi) * -direction,
+              lowerCircle.radius * math.sin(quarterPi),
+            ),
       );
-    // TODO(alestiago): Play with restitution value once game is bundled.
-    final kickerFixtureDef = FixtureDef(kicker)
+
+    final kickerFixtureDef = FixtureDef(kickerEdge)
+      // TODO(alestiago): Play with restitution value once game is bundled.
       ..restitution = 10.0
       ..friction = 0;
-    fixturesDef.add(kickerFixtureDef);
+    fixturesDefs.add(kickerFixtureDef);
+
+    // TODO(alestiago): Evaluate if there is value on centering the fixtures.
+    final centroid = geometry.centroid(
+      [
+        upperCircle.position + Vector2(0, -upperCircle.radius),
+        lowerCircle.position +
+            Vector2(
+              lowerCircle.radius * math.cos(quarterPi) * -direction,
+              -lowerCircle.radius * math.sin(quarterPi),
+            ),
+        wallFacingEdge.vertex2,
+      ],
+    );
+    for (final fixtureDef in fixturesDefs) {
+      if (fixtureDef.shape is EdgeShape) {
+        final edge = fixtureDef.shape as EdgeShape;
+        edge.set(edge.vertex1 - centroid, edge.vertex2 - centroid);
+      } else if (fixtureDef.shape is CircleShape) {
+        final circle = fixtureDef.shape as CircleShape;
+        circle.position.setFrom(circle.position - centroid);
+      }
+    }
 
-    return fixturesDef;
+    return fixturesDefs;
   }
 
   @override