var Present = Container.expand(function () {
	var self = Container.call(this);
	var presentGraphics = self.createAsset('present', 'Present Graphics', .5, .5);
	self.speed = -10;
	self.move = function () {
		self.y += self.speed;
	};
});
var NaughtyHouse = Container.expand(function () {
	var self = Container.call(this);
	var houseGraphics = self.createAsset('naughtyHouse', 'Naughty House Graphics', .5, .5);
	houseGraphics.tint = 0xFF0000;
	self.speed = 2;
	self.move = function () {
		self.y += self.speed;
		if (self.y > 2732 + self.height) {
			self.destroy();
		}
	};
});
var NiceHouse = Container.expand(function () {
	var self = Container.call(this);
	var houseGraphics = self.createAsset('niceHouse', 'Nice House Graphics', .5, .5);
	houseGraphics.tint = 0x00FF00;
	self.speed = 2;
	self.move = function () {
		self.y += self.speed;
		if (self.y > 2732 + self.height) {
			self.destroy();
		}
	};
});
var HappyHouse = Container.expand(function () {
	var self = Container.call(this);
	var houseGraphics = self.createAsset('happyHouse', 'Happy House Graphics', .5, .5);
	houseGraphics.tint = 0xFFFF00;
	self.speed = 2;
	self.move = function () {
		self.y += self.speed;
		if (self.y > 2732 + self.height) {
			self.destroy();
		}
	};
});
var DarkHouse = Container.expand(function () {
	var self = Container.call(this);
	var houseGraphics = self.createAsset('darkHouse', 'Dark House Graphics', .5, .5);
	houseGraphics.tint = 0x808080;
	self.speed = 2;
	self.move = function () {
		self.y += self.speed;
		if (self.y > 2732 + self.height) {
			self.destroy();
		}
	};
});
var Santa = Container.expand(function () {
	var self = Container.call(this);
	var santaGraphics = self.createAsset('santa', 'Santa Graphics', .5, .5);
	self.targetPosition = null;
	self.moveSpeed = 5;
	self.move = function (position) {
		if (position) {
			self.targetPosition = position;
		}
		if (self.targetPosition) {
			var dx = self.targetPosition.x - self.x;
			var dy = self.targetPosition.y - self.y;
			var distance = Math.sqrt(dx * dx + dy * dy);
			if (distance > 1) {
				var angle = Math.atan2(dy, dx);
				var tentativeX = self.x + Math.cos(angle) * self.moveSpeed;
				var tentativeY = self.y + Math.sin(angle) * self.moveSpeed;
				self.x = tentativeX;
				if (tentativeY > 2732 - 2732 / 3) {
					self.y = tentativeY;
				}
			} else {
				if (self.targetPosition.y > 2732 - 2732 / 3) {
					self.x = self.targetPosition.x;
					self.y = self.targetPosition.y;
				}
				self.targetPosition = null;
			}
		}
	};
});
var Game = Container.expand(function () {
	var self = Container.call(this);
	var houses = [];
	self.spawnHouse = function () {
		var nextSpawnTime = Math.random() * 1000 + 1000;
		var newHouseX = Math.random() * 2048;
		var newHouseY = -Math.random() * 500;
		var canSpawn = true;
		for (var i = 0; i < houses.length; i++) {
			var house = houses[i];
			if (Math.abs(newHouseX - house.x) < house.width && Math.abs(newHouseY - house.y) < house.height) {
				canSpawn = false;
				break;
			}
		}
		if (canSpawn) {
			var houseTypes = [NaughtyHouse, NiceHouse];
			var randomIndex = Math.random() < 0.34 ? 0 : 1;
			var house = new houseTypes[randomIndex]();
			house.x = newHouseX;
			house.y = newHouseY;
			houses.push(house);
			self.addChild(house);
		}
		LK.setTimeout(self.spawnHouse, nextSpawnTime);
	};
	self.spawnHouse();
	var houses = [];
	var presents = [];
	var santa = self.addChild(new Santa());
	santa.x = 2048 / 2;
	santa.y = 2732 - 2732 * 0.1;
	var presentFireRate = 60;
	var presentFireCounter = 0;
	stage.on('down', function (obj) {
		var pos = obj.event.getLocalPosition(self);
		santa.move(pos);
	});
	LK.on('tick', function () {
		santa.move();
		if (presentFireCounter++ >= presentFireRate) {
			var present = new Present();
			present.x = santa.x;
			present.y = santa.y;
			presents.push(present);
			self.addChild(present);
			presentFireCounter = 0;
		}
		for (var i = presents.length - 1; i >= 0; i--) {
			var present = presents[i];
			present.move();
			for (var j = houses.length - 1; j >= 0; j--) {
				var house = houses[j];
				if (house instanceof NaughtyHouse && present.intersects(house)) {
					var darkHouse = new DarkHouse();
					darkHouse.x = house.x;
					darkHouse.y = house.y;
					houses[j] = darkHouse;
					self.addChild(darkHouse);
					house.destroy();
					present.destroy();
					presents.splice(i, 1);
					break;
				}
			}
			if (present.y < -present.height) {
				present.destroy();
				presents.splice(i, 1);
			}
		}
		for (var i = houses.length - 1; i >= 0; i--) {
			var house = houses[i];
			house.move();
			if (house.y > 2732 + house.height) {
				houses.splice(i, 1);
			}
		}
	});
});

===================================================================
--- original.js
+++ change.js
@@ -7,15 +7,8 @@
 	};
 });
 var NaughtyHouse = Container.expand(function () {
 	var self = Container.call(this);
-	self.hitByPresent = function () {
-		var darkHouse = new DarkHouse();
-		darkHouse.x = self.x;
-		darkHouse.y = self.y;
-		self.parent.addChild(darkHouse);
-		self.destroy();
-	};
 	var houseGraphics = self.createAsset('naughtyHouse', 'Naughty House Graphics', .5, .5);
 	houseGraphics.tint = 0xFF0000;
 	self.speed = 2;
 	self.move = function () {
@@ -142,26 +135,30 @@
 		}
 		for (var i = presents.length - 1; i >= 0; i--) {
 			var present = presents[i];
 			present.move();
+			for (var j = houses.length - 1; j >= 0; j--) {
+				var house = houses[j];
+				if (house instanceof NaughtyHouse && present.intersects(house)) {
+					var darkHouse = new DarkHouse();
+					darkHouse.x = house.x;
+					darkHouse.y = house.y;
+					houses[j] = darkHouse;
+					self.addChild(darkHouse);
+					house.destroy();
+					present.destroy();
+					presents.splice(i, 1);
+					break;
+				}
+			}
 			if (present.y < -present.height) {
 				present.destroy();
 				presents.splice(i, 1);
 			}
 		}
 		for (var i = houses.length - 1; i >= 0; i--) {
 			var house = houses[i];
 			house.move();
-			for (var j = presents.length - 1; j >= 0; j--) {
-				var present = presents[j];
-				if (house instanceof NaughtyHouse && present.intersects(house)) {
-					house.hitByPresent();
-					houses.splice(i, 1);
-					present.destroy();
-					presents.splice(j, 1);
-					break;
-				}
-			}
 			if (house.y > 2732 + house.height) {
 				houses.splice(i, 1);
 			}
 		}