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 () {
		var currentTime = Date.now();
		self.frameCount++;
		var elapsedTime = (currentTime - self.lastTime) / 1000;
		if (elapsedTime >= 1) {
			self.framerate = self.frameCount / elapsedTime;
			self.updateDisplay();
			self.frameCount = 0;
			self.lastTime = currentTime;
		}
	};
});
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 = 0;
	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;
	var towerGraphics = self.createAsset('tower', 'Tower Graphics', .5, .5);
	self.cooldown = 0.625 / 0.7 * (1 / 0.6) * 1.3;
	self.cooldownTimer = 0;
	self.shoot = function (enemies, bullets) {
		this.handleShooting(enemies, bullets);
	};
	self.handleShooting = function (enemies, bullets) {
		self.cooldownTimer--;
		if (self.cooldownTimer <= 0 && enemies.length > 0) {
			self.fireBullet(bullets);
		}
	};
	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);
	var enemySpeed = 25.6 * 0.7 * 0.6;
	self.update = function () {
		self.y += enemySpeed;
		if (self.y > 2732) {
			self.game.destroyEnemy(self);
		}
	};
});
var Bullet = Container.expand(function (gameInstance) {
	var self = Container.call(this);
	self.game = gameInstance;
	var bulletGraphics = self.createAsset('bullet', 'Bullet Graphics', .5, .5);
	self.speed = 240;
	self.update = function () {
		self.y -= self.speed;
		if (self.y < 0) {
			self.game.removeBullet(self);
			self.destroy();
		}
	};
});
var Game = Container.expand(function () {
	var self = Container.call(this);
	self.destroyEnemy = function (enemy) {
		var index = self.enemies.indexOf(enemy);
		if (index > -1) {
			self.enemies.splice(index, 1);
			enemy.destroy();
		}
	};
	self.removeBullet = function (bullet) {
		var index = self.bullets.indexOf(bullet);
		if (index > -1) {
			self.bullets.splice(index, 1);
		}
	};
	self.removeEnemy = function (enemy) {
		var index = self.enemies.indexOf(enemy);
		if (index > -1) {
			self.enemies.splice(index, 1);
		}
	};
	self.incrementScore = function () {
		self.score++;
	};
	self.spawnEnemies = function () {
		this.generateEnemies();
	};
	self.generateEnemies = function () {
		enemiesSpawnedLastRound += 4;
		for (var i = 0; i < enemiesSpawnedLastRound; i++) {
			var newEnemy = new Enemy();
			newEnemy.x = Math.random() * 2048;
			newEnemy.y = -25 * (i + 1);
			self.enemies.push(newEnemy);
			self.addChild(newEnemy);
		}
		self.enemyCounterTxt.setText('Enemies: ' + self.enemies.length.toString());
	};
	self.updateEnemyCounter = function () {};
	self.score = 0;
	self.frameRateCounter = new FrameRateCounter();
	LK.gui.topRight.addChild(self.frameRateCounter.display);
	var enemiesSpawnedLastRound = 1;
	self.enemies = [];
	self.enemyCounterTxt = new Text2('Enemies: ' + self.enemies.length.toString(), {
		size: 150,
		fill: "#ff0000"
	});
	self.enemyCounterTxt.anchor.set(0, 1);
	LK.gui.bottomLeft.addChild(self.enemyCounterTxt);
	LK.stageContainer.setBackgroundColor(0xFFFFFF);
	var towers = [];
	self.bullets = [];
	self.bulletsContainer = self.addChild(new Container());
	self.enemies = [];
	var initialTower = new Tower(self);
	initialTower.x = 0 + initialTower.width / 2 - 260;
	initialTower.y = 500 + initialTower.height / 2 + 300 + 800 + 500;
	towers.push(initialTower);
	self.addChild(initialTower);
	var plain = self.addChild(new Plain());
	plain.x = 2048 / 2;
	plain.y = 2732 / 2;
	self.addChild(plain);
	var enemy = new Enemy();
	enemy.x = 2048 / 2;
	enemy.y = -enemy.height / 2;
	self.enemies.push(enemy);
	self.addChild(enemy);
	stage.on('down', function (obj) {
		var event = obj.event;
		var pos = event.getLocalPosition(self);
		var newTower = new Tower(self);
		newTower.x = pos.x;
		newTower.y = pos.y;
		self.addChild(newTower);
		towers.push(newTower);
	});
	LK.on('tick', function () {
		self.frameRateCounter.update(enemiesSpawnedLastRound);
		if (self.enemies.length === 0) {
			self.spawnEnemies();
		} else {
			towers.forEach(function (tower) {
				tower.shoot(self.enemies, self.bullets);
			});
		}
		self.enemies.forEach(function (enemy) {
			enemy.update();
		});
		self.bullets.forEach(function (bullet) {
			bullet.update();
			self.enemies.forEach(function (enemy, enemyIndex) {
				if (bullet.intersects(enemy)) {
					self.incrementScore();
					self.removeBullet(bullet);
					self.removeEnemy(enemy);
				}
			});
		});
	});
});

===================================================================
--- original.js
+++ change.js
@@ -71,9 +71,9 @@
 	var enemySpeed = 25.6 * 0.7 * 0.6;
 	self.update = function () {
 		self.y += enemySpeed;
 		if (self.y > 2732) {
-			gameInstance.destroyEnemy(self);
+			self.game.destroyEnemy(self);
 		}
 	};
 });
 var Bullet = Container.expand(function (gameInstance) {