docs: plunger issue comments

lib/game/components/plunger.dart

@@ -1,4 +1,3 @@
-import 'package:flame_forge2d/body_component.dart';
 import 'package:flame_forge2d/flame_forge2d.dart';
 
 class Plunger extends BodyComponent {
@@ -20,10 +19,12 @@ class Plunger extends BodyComponent {
     return world.createBody(bodyDef)..createFixture(fixtureDef);
   }
 
+  // Unused for now - from the previous kinematic plunger implementation.
   void pull() {
     body.linearVelocity = Vector2(0, -5);
   }
 
+  // Unused for now - from the previous kinematic plunger implementation.
   void release() {
     final velocity = (_position.y - body.position.y) * 9;
     body.linearVelocity = Vector2(0, velocity);

lib/game/pinball_game.dart

@@ -7,6 +7,7 @@ import 'package:pinball/game/game.dart';
 
 class PinballGame extends Forge2DGame with FlameBloc, KeyboardEvents {
   late Plunger plunger;
+  late PrismaticJointDef prismaticJointDef;
 
   @override
   Future<void> onLoad() async {
@@ -20,22 +21,30 @@ class PinballGame extends Forge2DGame with FlameBloc, KeyboardEvents {
 
     await add(plunger = Plunger(Vector2(center.x, center.y - 50)));
 
-    final prismaticJointDef = PrismaticJointDef()
+    prismaticJointDef = PrismaticJointDef()
       ..initialize(
         plunger.body,
         bottomWall.body,
-        bottomWall.body.position,
-        Vector2(0, 0),
+        plunger.body.position,
+        // Logically, I feel like this should be (0, 1), but it has to be
+        // negative for lowerTranslation limit to work as expected.
+        Vector2(0, -1),
       )
-      ..localAnchorA.setFrom(Vector2(0, 0))
       ..enableLimit = true
-      ..upperTranslation = 0
-      ..lowerTranslation = -5
+      // Given the above inverted vertical axis, the lowerTranslation works as
+      // expected and this lets the plunger fall down 10 units before being
+      // stopped.
+      //
+      // Ideally, we shouldn't need to set any limits here - this is just for
+      // demo purposes to see how the limits work. We should be leaving this at
+      // 0 and altering it as the user holds the space bar. The longer they hold
+      // it, the lower the lowerTranslation becomes - allowing the plunger to
+      // slowly fall down (see key event handlers below).
+      ..lowerTranslation = -10
+      // This prevents the plunger from falling through the bottom wall.
       ..collideConnected = true;
 
     world.createJoint(prismaticJointDef);
-    print(prismaticJointDef.localAnchorA);
-    print(prismaticJointDef.localAnchorB);
   }
 
   @override
@@ -45,11 +54,19 @@ class PinballGame extends Forge2DGame with FlameBloc, KeyboardEvents {
   ) {
     if (event is RawKeyUpEvent &&
         event.data.logicalKey == LogicalKeyboardKey.space) {
-      plunger.release();
+      // I haven't been able to successfully pull down the plunger, so this is
+      // completely untested. I imagine we could calculate the distance between
+      // the prismaticJoinDef.upperTranslation (plunger starting position) and
+      // the ground, then use that value as a multiplier on the speed so the
+      // ball moves faster when you pull the plunger farther down.
+      prismaticJointDef.motorSpeed = 5;
     }
     if (event is RawKeyDownEvent &&
         event.data.logicalKey == LogicalKeyboardKey.space) {
-      plunger.pull();
+      // This was my attempt to decrement the lower limit but it doesn't seem to
+      // render. If you debug, you can see that this value is being lowered,
+      // but the game isn't reflecting these value changes.
+      prismaticJointDef.lowerTranslation--;
     }
     return KeyEventResult.handled;
   }