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.hitCount = 0;
	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);
	function checkRankUp() {
		var xpThreshold = 6 * Math.pow(1.35, rank - 1);
		if (xp >= xpThreshold) {
			rank++;
			xp = 0;
			rankTxt.setText('Rank: ' + rank);
			updateXPDisplay();
		}
	}
	var countdown = 60;
	var score = 0;
	var scoreTxt = new Text2('Score: ' + score, {
		size: 75,
		fill: "#ffffff"
	});
	scoreTxt.anchor.set(0, 0);
	scoreTxt.x += 50;
	scoreTxt.y += 30;
	LK.gui.topLeft.addChild(scoreTxt);
	var timerTxt = new Text2(countdown.toString(), {
		size: 150,
		fill: "#ffffff"
	});
	timerTxt.anchor.set(.5, 0);
	LK.gui.topCenter.addChild(timerTxt);
	var xp = 0;
	var rank = 1;
	var rankTxt = new Text2('Rank: ' + rank, {
		size: 75,
		fill: "#ffffff"
	});
	rankTxt.anchor.set(0, 0);
	rankTxt.x = timerTxt.x + timerTxt.width + 230;
	rankTxt.y = scoreTxt.y;
	LK.gui.topCenter.addChild(rankTxt);
	var xpDisplayTxt = new Text2(xp + ' / ' + 6 * (rank - 1 + 1), {
		size: 75,
		fill: "#ffffff"
	});
	xpDisplayTxt.anchor.set(0, 0);
	xpDisplayTxt.x = rankTxt.x;
	xpDisplayTxt.y = rankTxt.y + rankTxt.height + 20;
	LK.gui.topCenter.addChild(xpDisplayTxt);
	function updateXPDisplay() {
		var xpThreshold = Math.floor(6 * Math.pow(1.35, rank - 1));
		xpDisplayTxt.setText(xp + ' / ' + xpThreshold);
	}
	function addXP(amount) {
		if (amount > 0) {
			xp += amount;
			checkRankUp();
		}
		updateXPDisplay();
	}
	var timer = LK.setInterval(function () {
		countdown--;
		timerTxt.setText(countdown.toString());
		if (countdown <= 0) {
			LK.clearInterval(timer);
			LK.showGameOver();
		}
	}, 1000);
	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();
					score = Math.max(0, score - 2);
					scoreTxt.setText('Score: ' + score);
					presents.splice(i, 1);
					break;
				} else if (house instanceof NiceHouse && present.intersects(house)) {
					house.hitCount++;
					score++;
					addXP(1);
					scoreTxt.setText('Score: ' + score);
					present.destroy();
					presents.splice(i, 1);
					if (house.hitCount >= 3) {
						var happyHouse = new HappyHouse();
						happyHouse.x = house.x;
						happyHouse.y = house.y;
						houses[j] = happyHouse;
						self.addChild(happyHouse);
						house.destroy();
					}
					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
@@ -87,8 +87,17 @@
 	};
 });
 var Game = Container.expand(function () {
 	var self = Container.call(this);
+	function checkRankUp() {
+		var xpThreshold = 6 * Math.pow(1.35, rank - 1);
+		if (xp >= xpThreshold) {
+			rank++;
+			xp = 0;
+			rankTxt.setText('Rank: ' + rank);
+			updateXPDisplay();
+		}
+	}
 	var countdown = 60;
 	var score = 0;
 	var scoreTxt = new Text2('Score: ' + score, {
 		size: 75,
@@ -122,29 +131,17 @@
 	xpDisplayTxt.x = rankTxt.x;
 	xpDisplayTxt.y = rankTxt.y + rankTxt.height + 20;
 	LK.gui.topCenter.addChild(xpDisplayTxt);
 	function updateXPDisplay() {
-		xpDisplayTxt.setText(xp + ' / ' + 6 * rank);
+		var xpThreshold = Math.floor(6 * Math.pow(1.35, rank - 1));
+		xpDisplayTxt.setText(xp + ' / ' + xpThreshold);
 	}
-	var oldUpdateRank = updateRank;
-	updateRank = function () {
-		oldUpdateRank();
-		updateXPDisplay();
-	};
-	function updateRank() {
-		var newRank = 1 + Math.floor(xp / 6);
-		if (newRank > rank) {
-			xp = 0;
-			updateXPDisplay();
-		}
-		rank = newRank;
-		rankTxt.setText('Rank: ' + rank);
-	}
 	function addXP(amount) {
 		if (amount > 0) {
 			xp += amount;
-			updateRank();
+			checkRankUp();
 		}
+		updateXPDisplay();
 	}
 	var timer = LK.setInterval(function () {
 		countdown--;
 		timerTxt.setText(countdown.toString());