/**** 
* Classes
****/
var FrameRateCounter = Container.expand(function () {
	var self = Container.call(this);
	self.lastTime = Date.now();
	self.frameCount = 0;
	self.framerate = 0;
	self.display = new Text2('FPS: 0', {
		size: 150,
		fill: '#000000'
	});
	self.display.anchor.set(1, 0);
	self.updateDisplay = function () {
		self.display.setText('FPS: ' + Math.round(self.framerate).toString());
	};
	self.update = function (timestamp) {
		if (!self.lastTime) {
			self.lastTime = timestamp;
		}
		var delta = timestamp - self.lastTime;
		self.frameCount++;
		if (delta >= 1000) {
			self.framerate = self.frameCount;
			self.updateDisplay();
			self.frameCount = 0;
			self.lastTime = timestamp;
		}
		// LK engine's tick event replaces requestAnimationFrame
		LK.on('tick', self.update);
	};
});
var Plain = Container.expand(function () {
	var self = Container.call(this);
	var plainGraphics = self.createAsset('correct_plain_asset_id', 'Correct Plain Graphics Description', .5, .5);
	plainGraphics.scale.x = 2;
	plainGraphics.scale.y = 2;
	plainGraphics.alpha = 1;
	self.shoot = function (enemies, bulletsContainer) {
		if (self.cooldownTimer <= 0 && enemies.length > 0) {
			var bullet = new Bullet(self);
			bullet.x = self.x;
			bullet.y = self.y;
			bulletsContainer.addChild(bullet);
			self.cooldownTimer = self.cooldown;
		}
		self.cooldownTimer--;
	};
});
var Tower = Container.expand(function (gameInstance) {
	var self = Container.call(this);
	self.game = gameInstance;
	self.game = gameInstance;
	var towerGraphics = self.createAsset('tower', 'Tower Graphics', .5, .5);
	self.cooldown = 2.5;
	self.cooldownTimer = 0;
	self.shoot = function (enemies, bullets) {
		if (self.cooldownTimer <= 0 && enemies.length > 0) {
			self.fireBullet(bullets);
		}
		self.cooldownTimer--;
	};
	self.fireBullet = function (bullets) {
		var bullet = new Bullet(self.game);
		bullet.x = self.x;
		bullet.y = self.y;
		gameInstance.bulletsContainer.addChild(bullet);
		gameInstance.bullets.push(bullet);
		self.cooldownTimer = self.cooldown;
	};
});
var Enemy = Container.expand(function (gameInstance) {
	var self = Container.call(this);
	self.game = gameInstance;
	var enemyGraphics = self.createAsset('enemy', 'Enemy Graphics', .5, .5);
	self.move = function () {
		self.y += 12.8;
		if (self.y > 2732) {
			self.destroy();
		}
	};
});
var Bullet = Container.expand(function (gameInstance) {
	var self = Container.call(this);
	self.game = gameInstance;
	self.game = gameInstance;
	var bulletGraphics = self.createAsset('bullet', 'Bullet Graphics', .5, .5);
	self.move = function () {
		self.x += 120;
		if (self.x > 2048) {
			self.destroy();
		}
	};
});

/**** 
* Initialize Game
****/
var game = new LK.Game({
	backgroundColor: 0x000000
});

/**** 
* Game Code
****/
game.spawnEnemies = function () {
	enemiesSpawnedLastRound += 6;
	for (var i = 0; i < enemiesSpawnedLastRound; i++) {
		var newEnemy = new Enemy();
		newEnemy.x = Math.random() * 2048;
		newEnemy.y = -50 * (i + 1);
		game.enemies.push(newEnemy);
		game.addChild(newEnemy);
	}
	game.enemyCounterTxt.setText('Enemies: ' + game.enemies.length.toString());
};
game.updateEnemyCounter = function () {};
game.score = 0;
game.gold = 100;
game.incrementScore = function () {
	this.score++;
};
game.frameRateCounter = new FrameRateCounter();
LK.gui.topRight.addChild(game.frameRateCounter.display);
var enemiesSpawnedLastRound = 1;
game.scoreTxt = new Text2(game.score.toString(), {
	size: 150,
	fill: "#ffffff"
});
game.scoreTxt.anchor.set(0.5, 0);
LK.gui.topCenter.addChild(game.scoreTxt);
game.goldTxt = new Text2(game.gold.toString(), {
	size: 150,
	fill: "#ffff00"
});
game.goldTxt.anchor.set(0, 0);
LK.gui.topLeft.addChild(game.goldTxt);
game.enemies = [];
game.enemyCounterTxt = new Text2('Enemies: ' + game.enemies.length.toString(), {
	size: 150,
	fill: "#ff0000"
});
game.enemyCounterTxt.anchor.set(0, 1);
LK.gui.bottomLeft.addChild(game.enemyCounterTxt);
game.setBackgroundColor(0xFFFFFF);
var towers = [];
game.bullets = [];
game.bulletsContainer = game.addChild(new Container());
game.enemies = [];
var initialTower = new Tower(game);
initialTower.x = 0 + initialTower.width / 2 - 130;
initialTower.y = 500 + initialTower.height / 2 + 300;
towers.push(initialTower);
game.addChild(initialTower);
var plain = game.addChild(new Plain());
plain.x = 2048 / 2;
plain.y = 2732 / 2;
game.addChild(plain);
var enemy = new Enemy();
enemy.x = 2048 / 2;
enemy.y = -enemy.height / 2;
game.enemies.push(enemy);
game.addChild(enemy);
game.on('down', function (obj) {
	var event = obj.event;
	var pos = event.getLocalPosition(game);
	if (game.gold >= 50) {
		var newTower = new Tower(game);
		newTower.x = pos.x;
		newTower.y = pos.y;
		game.addChild(newTower);
		towers.push(newTower);
		game.gold -= 50;
		game.goldTxt.setText(game.gold.toString());
	}
});
LK.on('tick', function () {
	game.frameRateCounter.update();
	if (game.enemies.length === 0) {
		game.spawnEnemies();
	} else {
		towers.forEach(function (tower) {
			tower.shoot(game.enemies, game.bullets);
		});
	}
	game.enemies.forEach(function (enemy) {
		enemy.move();
	});
	game.bullets.forEach(function (bullet, index) {
		bullet.move();
		for (var j = game.enemies.length - 1; j >= 0; j--) {
			if (bullet.intersects(game.enemies[j])) {
				game.enemies[j].destroy();
				game.enemies.splice(j, 1);
				game.incrementScore();
				game.scoreTxt.setText(game.score.toString());
				game.gold += 50;
				bullet.destroy();
				game.enemyCounterTxt.setText('Enemies: ' + game.enemies.length.toString());
				break;
			}
		}
		if (bullet.x > 2048) {
			bullet.destroy();
			game.bullets.splice(index, 1);
		}
	});
});

===================================================================
--- original.js
+++ change.js
@@ -25,9 +25,10 @@
 			self.updateDisplay();
 			self.frameCount = 0;
 			self.lastTime = timestamp;
 		}
-		requestAnimationFrame(self.update);
+		// LK engine's tick event replaces requestAnimationFrame
+		LK.on('tick', self.update);
 	};
 });
 var Plain = Container.expand(function () {
 	var self = Container.call(this);