refactor: rampopening with layered mixin

lib/game/components/jetpack_ramp.dart

@@ -47,11 +47,15 @@ class JetpackRamp extends Component with HasGameRef<PinballGame> {
     final leftOpening = JetpackRampOpening(
       orientation: RampOrientation.down,
       rotation: radians(15),
-    )..initialPosition = position + Vector2(-11, 1);
+    )
+      ..initialPosition = position + Vector2(-11, 1)
+      ..layer = Layer.opening;
     final rightOpening = JetpackRampOpening(
       orientation: RampOrientation.down,
       rotation: radians(-9),
-    )..initialPosition = position + Vector2(20.5, 3.4);
+    )
+      ..initialPosition = position + Vector2(20.5, 3.4)
+      ..layer = Layer.opening;
 
     await addAll([
       curvePath,
@@ -74,7 +78,6 @@ class JetpackRampOpening extends RampOpening {
         _orientation = orientation,
         super(
           pathwayLayer: Layer.jetpack,
-          openingLayer: Layer.opening,
         );
 
   /// Orientation of entrance/exit of [JetpackRamp] where

lib/game/components/launcher_ramp.dart

@@ -52,10 +52,14 @@ class LauncherRamp extends Component with HasGameRef<PinballGame> {
     final leftOpening = LauncherRampOpening(
       orientation: RampOrientation.down,
       rotation: radians(13),
-    )..initialPosition = position + Vector2(-46.5, -8.5);
+    )
+      ..initialPosition = position + Vector2(-46.5, -8.5)
+      ..layer = Layer.opening;
     final rightOpening = LauncherRampOpening(
       orientation: RampOrientation.down,
-    )..initialPosition = position + Vector2(4, 0);
+    )
+      ..initialPosition = position + Vector2(4, 0)
+      ..layer = Layer.opening;
 
     await addAll([
       straightPath,
@@ -79,7 +83,6 @@ class LauncherRampOpening extends RampOpening {
         _orientation = orientation,
         super(
           pathwayLayer: Layer.launcher,
-          openingLayer: Layer.opening,
         );
 
   /// Orientation of entrance/exit of [LauncherRamp] where

lib/game/components/ramp_opening.dart

@@ -21,20 +21,15 @@ enum RampOrientation {
 /// through this opening. By default openings are [Layer.board] that
 /// means opening are at ground level, not over board.
 /// {@endtemplate}
-abstract class RampOpening extends BodyComponent with InitialPosition {
+abstract class RampOpening extends BodyComponent with InitialPosition, Layered {
   /// {@macro ramp_opening}
   RampOpening({
     required Layer pathwayLayer,
-    Layer? openingLayer,
+  }) : _pathwayLayer = pathwayLayer {
-  })  : _pathwayLayer = pathwayLayer,
+    layer = Layer.board;
-        _openingLayer = openingLayer ?? Layer.board;
+  }
-
-  final Layer _openingLayer;
   final Layer _pathwayLayer;
 
-  /// Mask of category bits for collision with [RampOpening].
-  Layer get openingLayer => _openingLayer;
-
   /// Mask of category bits for collision inside [Pathway].
   Layer get pathwayLayer => _pathwayLayer;
 
@@ -48,9 +43,7 @@ abstract class RampOpening extends BodyComponent with InitialPosition {
 
   @override
   Body createBody() {
-    final fixtureDef = FixtureDef(shape)
+    final fixtureDef = FixtureDef(shape)..isSensor = true;
-      ..isSensor = true
-      ..filter.categoryBits = _openingLayer.maskBits;
 
     final bodyDef = BodyDef()
       ..userData = this