refactor: modified jetpack ramp to use shapes and blueprint

lib/game/components/jetpack_ramp.dart

@@ -10,10 +10,14 @@ import 'package:pinball/flame/blueprint.dart';
 import 'package:pinball/game/game.dart';
 import 'package:pinball_components/pinball_components.dart';
 
-/// {@template jetpack_ramp}
-/// Represents the upper left blue ramp of the [Board].
-/// {@endtemplate}
+/// A [Blueprint] which creates the [JetpackRamp].
 class Jetpack extends Forge2DBlueprint {
+  /// Width between walls of the [Pathway].
+  static const width = 5.0;
+
+  /// Size for the radius of the external wall [Pathway].
+  static const externalRadius = 18.0;
+
   @override
   void build(_) {
     final position = Vector2(
@@ -33,9 +37,8 @@ class Jetpack extends Forge2DBlueprint {
       ..layer = Layer.jetpack;
 
     final _curve = JetpackRamp()
-      ..initialPosition = position
+      ..initialPosition = position + Vector2(5, -20.2)
       ..layer = Layer.jetpack;
-
     final _rightOpening = _JetpackRampOpening(
       rotation: math.pi,
     )
@@ -50,6 +53,9 @@ class Jetpack extends Forge2DBlueprint {
   }
 }
 
+/// {@template jetpack_ramp}
+/// Represents the upper left blue ramp of the [Board].
+/// {@endtemplate}
 class JetpackRamp extends BodyComponent with InitialPosition, Layered {
   JetpackRamp() : super(priority: 2) {
     layer = Layer.jetpack;
@@ -58,23 +64,37 @@ class JetpackRamp extends BodyComponent with InitialPosition, Layered {
       ..style = PaintingStyle.stroke;
   }
 
-  @override
-  Body createBody() {
-    final curveShape = ArcShape(
+  List<FixtureDef> _createFixtureDefs() {
+    final fixturesDef = <FixtureDef>[];
+
+    final externalCurveShape = ArcShape(
       center: initialPosition,
-      arcRadius: 18,
+      arcRadius: Jetpack.externalRadius,
       angle: math.pi,
       rotation: math.pi,
     );
+    final externalFixtureDef = FixtureDef(externalCurveShape);
+    fixturesDef.add(externalFixtureDef);
 
+    final internalCurveShape = externalCurveShape.copyWith(
+      arcRadius: Jetpack.externalRadius - Jetpack.width,
+    );
+    final internalFixtureDef = FixtureDef(internalCurveShape);
+    fixturesDef.add(internalFixtureDef);
+
+    return fixturesDef;
+  }
+
+  @override
+  Body createBody() {
     final bodyDef = BodyDef()
       ..userData = this
       ..position = initialPosition;
 
-    return world.createBody(bodyDef)
-      ..createFixture(
-        FixtureDef(curveShape),
-      );
+    final body = world.createBody(bodyDef);
+    _createFixtureDefs().forEach(body.createFixture);
+
+    return body;
   }
 }
 
@@ -96,9 +116,7 @@ class _JetpackRampOpening extends RampOpening {
 
   final double _rotation;
 
-  // TODO(ruialonso): Avoid magic number 3, should be propotional to
-  // [JetpackRamp].
-  static final Vector2 _size = Vector2(3, .1);
+  static final Vector2 _size = Vector2(Jetpack.width / 3, .1);
 
   @override
   Shape get shape => PolygonShape()