/**** 
* Classes
****/ 
// Asteroid class
var Asteroid = Container.expand(function () {
	var self = Container.call(this);
	var asteroidGraphics = self.attachAsset('asteroid', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 7;
	self.update = function () {
		self.y += self.speed;
		if (self.y > 2732 + asteroidGraphics.height) {
			self.destroy();
			asteroids.splice(asteroids.indexOf(self), 1);
		}
	};
});
// Enemy class
var Enemy = Container.expand(function () {
	var self = Container.call(this);
	var enemyGraphics = self.attachAsset('enemy', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 5;
	self.update = function () {
		self.y += self.speed;
		if (self.y > 2732 + enemyGraphics.height) {
			self.destroy();
			enemies.splice(enemies.indexOf(self), 1);
		}
	};
});
//<Assets used in the game will automatically appear here>
// Hero class
var Hero = Container.expand(function () {
	var self = Container.call(this);
	var heroGraphics = self.attachAsset('hero', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 10;
	self.update = function () {
		// Hero update logic
	};
	self.shoot = function () {
		var bullet = new HeroBullet();
		bullet.x = self.x;
		bullet.y = self.y - heroGraphics.height / 2;
		game.addChild(bullet);
		heroBullets.push(bullet);
	};
});
// HeroBullet class
var HeroBullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.attachAsset('heroBullet', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = -15;
	self.update = function () {
		self.y += self.speed;
		if (self.y < -bulletGraphics.height) {
			self.destroy();
			heroBullets.splice(heroBullets.indexOf(self), 1);
		}
	};
});
var StarBackground = Container.expand(function () {
	var self = Container.call(this);
	var background = self.attachAsset('starBackground', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 2;
	self.update = function () {
		self.y += self.speed;
		if (self.y > 2732) {
			self.y = 0;
		}
	};
});

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

/**** 
* Game Code
****/ 
// Initialize star background
var starBackground = new StarBackground();
starBackground.x = 2048 / 2;
starBackground.y = 0;
game.addChild(starBackground);
// Initialize arrays and variables
var hero;
var heroBullets = [];
var enemies = [];
var asteroids = [];
var score = 0;
var scoreTxt = new Text2('0', {
	size: 150,
	fill: "#ffffff"
});
scoreTxt.anchor.set(0.5, 0);
LK.gui.top.addChild(scoreTxt);
// Initialize hero
hero = new Hero();
hero.x = 2048 / 2;
hero.y = 2732 - 200;
game.addChild(hero);
// Handle game events
game.down = function (x, y, obj) {
	hero.x = x;
	hero.y = y;
};
game.move = function (x, y, obj) {
	hero.x = x;
	hero.y = y;
};
game.update = function () {
	// Update star background
	starBackground.update();
	// Update hero bullets
	for (var i = heroBullets.length - 1; i >= 0; i--) {
		heroBullets[i].update();
	}
	// Update enemies
	for (var j = enemies.length - 1; j >= 0; j--) {
		enemies[j].update();
		if (hero.intersects(enemies[j])) {
			LK.effects.flashScreen(0xff0000, 1000);
			LK.showGameOver();
		}
	}
	// Update asteroids
	for (var k = asteroids.length - 1; k >= 0; k--) {
		asteroids[k].update();
		if (hero.intersects(asteroids[k])) {
			LK.effects.flashScreen(0xff0000, 1000);
			LK.showGameOver();
		}
	}
	// Spawn enemies
	if (LK.ticks % 60 == 0) {
		var enemy = new Enemy();
		enemy.x = Math.random() * 2048;
		enemy.y = -enemy.height;
		game.addChild(enemy);
		enemies.push(enemy);
	}
	// Spawn asteroids
	if (LK.ticks % 180 == 0) {
		var asteroid = new Asteroid();
		asteroid.x = Math.random() * 2048;
		asteroid.y = -asteroid.height;
		game.addChild(asteroid);
		asteroids.push(asteroid);
	}
	// Update score
	scoreTxt.setText(score);
};
// Shoot bullets
game.down = function (x, y, obj) {
	hero.shoot();
};

===================================================================
--- original.js
+++ change.js
@@ -68,8 +68,22 @@
 			heroBullets.splice(heroBullets.indexOf(self), 1);
 		}
 	};
 });
+var StarBackground = Container.expand(function () {
+	var self = Container.call(this);
+	var background = self.attachAsset('starBackground', {
+		anchorX: 0.5,
+		anchorY: 0.5
+	});
+	self.speed = 2;
+	self.update = function () {
+		self.y += self.speed;
+		if (self.y > 2732) {
+			self.y = 0;
+		}
+	};
+});
 
 /**** 
 * Initialize Game
 ****/ 
@@ -79,8 +93,13 @@
 
 /**** 
 * Game Code
 ****/ 
+// Initialize star background
+var starBackground = new StarBackground();
+starBackground.x = 2048 / 2;
+starBackground.y = 0;
+game.addChild(starBackground);
 // Initialize arrays and variables
 var hero;
 var heroBullets = [];
 var enemies = [];
@@ -106,8 +125,10 @@
 	hero.x = x;
 	hero.y = y;
 };
 game.update = function () {
+	// Update star background
+	starBackground.update();
 	// Update hero bullets
 	for (var i = heroBullets.length - 1; i >= 0; i--) {
 		heroBullets[i].update();
 	}