Massively improve collision detection by colliding the shuttlecock wi…

…th a polygon containing all space the battledore has travelled through during the previous frame.

src/net/noiseinstitute/battledore_and_shuttlecock/Battledore.as

@@ -7,16 +7,23 @@ package net.noiseinstitute.battledore_and_shuttlecock {
 
     public class Battledore extends Entity {
         public var offsetX:Number = 0;
+
         public var prevX:Number = 0;
         public var prevY:Number = 0;
+
+        public var battledoreWidth:Number = 8;
+        public var battledoreHeight:Number = 64;
+
         public var velocity:Point = new Point;
 
+        private var battledoreMask:BattledoreMask;
+
         public function Battledore() {
-            var image:Image = Image.createRect(8, 64);
+            var image:Image = Image.createRect(battledoreWidth, battledoreHeight);
             image.centerOrigin();
             graphic = image;
 
-            setHitbox(image.width, image.height, image.originX, image.originY);
+            mask = battledoreMask = new BattledoreMask(this);
         }
 
         override public function update():void {
@@ -29,6 +36,8 @@ package net.noiseinstitute.battledore_and_shuttlecock {
             velocity.x = x - prevX;
             velocity.y = y - prevY;
 
+            battledoreMask.updateMask();
+
             super.update();
         }
     }

src/net/noiseinstitute/battledore_and_shuttlecock/BattledoreMask.as

@@ -0,0 +1,92 @@
+package net.noiseinstitute.battledore_and_shuttlecock {
+    import flash.display.Graphics;
+    import flash.display.Sprite;
+
+    import net.flashpunk.FP;
+    import net.flashpunk.Mask;
+
+    public class BattledoreMask extends Mask {
+        private var battledore:Battledore;
+
+        private var collisionContainer:Sprite = new Sprite();
+        private var mask:Sprite = new Sprite();
+        private var hitObject:Sprite = new Sprite();
+
+        public function BattledoreMask(battledore:Battledore) {
+            this.battledore = battledore;
+
+            collisionContainer.addChild(mask);
+            collisionContainer.addChild(hitObject);
+
+            _check[Mask] = collideMask;
+        }
+
+        public function updateMask():void {
+            update();
+
+            var halfWidth:Number = battledore.battledoreWidth * 0.5;
+            var halfHeight:Number = battledore.battledoreHeight * 0.5;
+
+            var graphics:Graphics = mask.graphics;
+            graphics.clear();
+            graphics.lineStyle();
+
+            graphics.beginFill(0xffffff, 1);
+            graphics.moveTo(battledore.prevX - halfWidth, battledore.prevY - halfHeight);
+            graphics.lineTo(battledore.x - halfWidth, battledore.y - halfHeight);
+            graphics.lineTo(battledore.x + halfWidth, battledore.y - halfHeight);
+            graphics.lineTo(battledore.prevX + halfWidth, battledore.prevY - halfHeight);
+            graphics.lineTo(battledore.prevX - halfWidth, battledore.prevY - halfHeight);
+            graphics.endFill();
+
+            graphics.beginFill(0xff0000, 1);
+            graphics.moveTo(battledore.prevX + halfWidth, battledore.prevY - halfHeight);
+            graphics.lineTo(battledore.x + halfWidth, battledore.y - halfHeight);
+            graphics.lineTo(battledore.x + halfWidth, battledore.y + halfHeight);
+            graphics.lineTo(battledore.prevX + halfWidth, battledore.prevY + halfHeight);
+            graphics.lineTo(battledore.prevX + halfWidth, battledore.prevY - halfHeight);
+            graphics.endFill();
+
+            graphics.beginFill(0x00ff00, 1);
+            graphics.moveTo(battledore.prevX + halfWidth, battledore.prevY + halfHeight);
+            graphics.lineTo(battledore.x + halfWidth, battledore.y + halfHeight);
+            graphics.lineTo(battledore.x - halfWidth, battledore.y + halfHeight);
+            graphics.lineTo(battledore.prevX - halfWidth, battledore.prevY + halfHeight);
+            graphics.lineTo(battledore.prevX + halfWidth, battledore.prevY + halfHeight);
+            graphics.endFill();
+
+            graphics.beginFill(0x0000ff, 1);
+            graphics.moveTo(battledore.prevX - halfWidth, battledore.prevY + halfHeight);
+            graphics.lineTo(battledore.x - halfWidth, battledore.y + halfHeight);
+            graphics.lineTo(battledore.x - halfWidth, battledore.y - halfHeight);
+            graphics.lineTo(battledore.prevX - halfWidth, battledore.prevY - halfHeight);
+            graphics.lineTo(battledore.prevX - halfWidth, battledore.prevY + halfHeight);
+            graphics.endFill();
+        }
+
+        override protected function update():void {
+            parent.originX = parent.x;
+            parent.originY = parent.y;
+            parent.width = Main.WIDTH;
+            parent.height = Main.HEIGHT;
+        }
+
+        private function collideMask(other:Mask):Boolean {
+            var graphics:Graphics = hitObject.graphics;
+            graphics.clear();
+            graphics.beginFill(0xffff00, 1);
+            graphics.drawRect(other.parent.x - other.parent.originX,
+                    other.parent.y - other.parent.originY,
+                    other.parent.width,
+                    other.parent.height);
+            graphics.endFill();
+
+            return mask.hitTestObject(hitObject);
+        }
+
+        override public function renderDebug(g:Graphics):void {
+            FP.engine.alpha = 0.5;
+            FP.stage.addChild(collisionContainer);
+        }
+    }
+}

src/net/noiseinstitute/battledore_and_shuttlecock/GameWorld.as

@@ -92,15 +92,15 @@ package net.noiseinstitute.battledore_and_shuttlecock {
             updateScore(score+1);
 
             if (shuttlecock.x > battledore.prevX) {
-                if (shuttlecock.x < battledore.x + (shuttlecock.width + battledore.width) * 0.5 + 1) {
-                    shuttlecock.x = battledore.x + (shuttlecock.width + battledore.width) * 0.5 + 1;
+                if (shuttlecock.x < battledore.x + (shuttlecock.width + battledore.battledoreWidth) * 0.5 + 1) {
+                    shuttlecock.x = battledore.x + (shuttlecock.width + battledore.battledoreWidth) * 0.5 + 1;
                 }
                 if (shuttlecock.velocity.x < 0) {
                     shuttlecock.velocity.x = -shuttlecock.velocity.x;
                 }
             } else {
-                if (shuttlecock.x > battledore.x - (shuttlecock.width + battledore.width) * 0.5 - 1) {
-                    shuttlecock.x = battledore.x - (shuttlecock.width + battledore.width) * 0.5 -1;
+                if (shuttlecock.x > battledore.x - (shuttlecock.width + battledore.battledoreWidth) * 0.5 - 1) {
+                    shuttlecock.x = battledore.x - (shuttlecock.width + battledore.battledoreWidth) * 0.5 -1;
                 }
                 if (shuttlecock.velocity.x > 0) {
                     shuttlecock.velocity.x = -shuttlecock.velocity.x;