/**** 
* Classes
****/
// Enemy class
var Enemy = Container.expand(function () {
	var self = Container.call(this);
	var enemyGraphics = self.createAsset('enemy', 'Enemy Ship', 0.5, 0.5);
	self.speed = 2;
	self.move = function () {
		self.y += self.speed;
	};
	self.isOffScreen = function () {
		return self.y > 2732 + self.height;
	};
});
// Hero class
var Hero = Container.expand(function () {
	var self = Container.call(this);
	var heroGraphics = self.createAsset('hero', 'Hero Ship', 0.5, 0.5);
	self.x = 2048 / 2;
	self.y = 2732 - 200;
});
// Bullet class
var Bullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.createAsset('bullet', 'Bullet', 0.5, 0.5);
	self.speed = -10;
	self.move = function () {
		self.y += self.speed;
	};
	self.isOffScreen = function () {
		return self.y < -self.height;
	};
});
// EnemyBullet class
var EnemyBullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.createAsset('enemyBullet', 'Enemy Bullet', 0.5, 0.5);
	self.speed = 5;
	self.move = function () {
		self.y += self.speed;
	};
	self.isOffScreen = function () {
		return self.y > 2732 + self.height;
	};
});

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

/**** 
* Game Code
****/
// Initialize hero
var hero = game.addChild(new Hero());
// Initialize enemy and bullet arrays
var enemies = [];
var heroBullets = [];
var enemyBullets = [];
// Game state
var isGameOver = false;
// Touch event handling
var dragNode = null;
function handleMove(obj) {
	var event = obj.event;
	var pos = event.getLocalPosition(game);
	if (dragNode) {
		dragNode.x = pos.x;
		dragNode.y = pos.y;
	}
}
game.on('down', function (obj) {
	dragNode = hero;
	handleMove(obj);
});
game.on('move', handleMove);
game.on('up', function (obj) {
	dragNode = null;
});
// Game tick event
LK.on('tick', function () {
	if (isGameOver) {
		LK.effects.flashScreen(0xff0000, 1000);
		LK.showGameOver();
		return;
	}
	// Move hero bullets
	for (var i = heroBullets.length - 1; i >= 0; i--) {
		heroBullets[i].move();
		if (heroBullets[i].isOffScreen()) {
			heroBullets[i].destroy();
			heroBullets.splice(i, 1);
		}
	}
	// Move enemies and enemy bullets
	for (var j = enemies.length - 1; j >= 0; j--) {
		enemies[j].move();
		if (enemies[j].isOffScreen()) {
			enemies[j].destroy();
			enemies.splice(j, 1);
		}
	}
	if (enemyBullets) {
		for (var m = enemyBullets.length - 1; m >= 0; m--) {
			enemyBullets[m].move();
			if (enemyBullets[m].isOffScreen()) {
				enemyBullets[m].destroy();
				enemyBullets.splice(m, 1);
			}
		}
	}
	// Check for collisions
	for (var k = heroBullets.length - 1; k >= 0; k--) {
		for (var l = enemies.length - 1; l >= 0; l--) {
			if (heroBullets[k].intersects(enemies[l])) {
				heroBullets[k].destroy();
				heroBullets.splice(k, 1);
				enemies[l].destroy();
				enemies.splice(l, 1);
				break;
			}
		}
	}
	// Fire bullets
	if (LK.ticks % 30 == 0) {
		var bullet = new Bullet();
		bullet.x = hero.x;
		bullet.y = hero.y;
		heroBullets.push(bullet);
		game.addChild(bullet);
	}
	// Spawn enemies and make them shoot bullets
	// Moved enemyBullets array declaration to the top of the game code to persist its state
	if (LK.ticks % 120 == 0) {
		var enemy = new Enemy();
		enemy.x = Math.random() * (2048 - enemy.width) + enemy.width / 2;
		enemy.y = -enemy.height;
		enemies.push(enemy);
		game.addChild(enemy);
	}
	// Enemies shoot bullets
	if (LK.ticks % 60 == 0) {
		enemies.forEach(function (enemy) {
			var enemyBullet = new EnemyBullet();
			enemyBullet.x = enemy.x;
			enemyBullet.y = enemy.y + enemy.height / 2;
			enemyBullets.push(enemyBullet);
			game.addChild(enemyBullet);
		});
	}
});

===================================================================
--- original.js
+++ change.js
@@ -103,13 +103,15 @@
 			enemies[j].destroy();
 			enemies.splice(j, 1);
 		}
 	}
-	for (var m = enemyBullets.length - 1; m >= 0; m--) {
-		enemyBullets[m].move();
-		if (enemyBullets[m].isOffScreen()) {
-			enemyBullets[m].destroy();
-			enemyBullets.splice(m, 1);
+	if (enemyBullets) {
+		for (var m = enemyBullets.length - 1; m >= 0; m--) {
+			enemyBullets[m].move();
+			if (enemyBullets[m].isOffScreen()) {
+				enemyBullets[m].destroy();
+				enemyBullets.splice(m, 1);
+			}
 		}
 	}
 	// Check for collisions
 	for (var k = heroBullets.length - 1; k >= 0; k--) {
@@ -131,9 +133,9 @@
 		heroBullets.push(bullet);
 		game.addChild(bullet);
 	}
 	// Spawn enemies and make them shoot bullets
-	// Moved enemyBullets array declaration to the top of the game code
+	// Moved enemyBullets array declaration to the top of the game code to persist its state
 	if (LK.ticks % 120 == 0) {
 		var enemy = new Enemy();
 		enemy.x = Math.random() * (2048 - enemy.width) + enemy.width / 2;
 		enemy.y = -enemy.height;