/**** 
* Classes
****/ 
var Bullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.attachAsset('bullet', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 5;
	self.update = function () {
		self.x += self.speed;
		if (self.x < 0) {
			self.destroy();
		}
	};
});
var Enemy = Container.expand(function () {
	var self = Container.call(this);
	var enemyGraphics = self.attachAsset('enemy', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = -3;
	self.update = function () {
		self.x += self.speed;
		if (self.x < 0 || self.x > 2048) {
			self.destroy();
		}
	};
});
var Ground = Container.expand(function () {
	var self = Container.call(this);
	var groundGraphics = self.attachAsset('ground', {
		anchorX: 0.5,
		anchorY: 0.5,
		scaleX: 3,
		// Scale horizontally by 1.2
		scaleY: 3 // Scale vertically by 1.2
	});
	self.update = function () {
		// Ground moves from right to left
		self.x -= 5;
		if (self.x + self.width < 0) {
			self.x = 2048;
		}
	};
});
var Player = Container.expand(function () {
	var self = Container.call(this);
	var playerGraphics = self.attachAsset('player', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 5;
	self.update = function () {
		if (self.x < 0) {
			self.x = 0;
		}
		if (self.x > 300) {
			self.x = 300;
		}
		// Player only moves horizontally
	};
});

/**** 
* Initialize Game
****/ 
var game = new LK.Game();

/**** 
* Game Code
****/ 
var background1 = game.addChild(LK.getAsset('background', {
	anchorX: 0.5,
	anchorY: 0.5,
	x: 1024,
	y: 1366,
	width: 2048,
	height: 2732
}));
var background2 = game.addChild(LK.getAsset('background', {
	anchorX: 0.5,
	anchorY: 0.5,
	x: 3072,
	y: 1366,
	width: 2048,
	height: 2732
}));
var ground = game.addChild(new Ground());
ground.x = 1024;
ground.y = 2732 - 200; // Move the ground asset a little bit up from the bottom of the screen
var player = game.addChild(new Player());
player.x = 1024;
player.y = ground.y - 150;
var enemies = [];
var bullets = [];
game.update = function () {
	background1.x -= 5;
	background2.x -= 5;
	if (background1.x <= -1024) {
		background1.x = background2.x + 2048;
	}
	if (background2.x <= -1024) {
		background2.x = background1.x + 2048;
	}
	if (LK.ticks % 60 == 0) {
		var enemy = game.addChild(new Enemy());
		enemy.x = 2048;
		enemy.y = Math.random() * 2732;
		enemies.push(enemy);
	}
	for (var i = bullets.length - 1; i >= 0; i--) {
		var bullet = bullets[i];
		for (var j = enemies.length - 1; j >= 0; j--) {
			var enemy = enemies[j];
			if (bullet.intersects(enemy)) {
				bullet.destroy();
				bullets.splice(i, 1);
				enemy.destroy();
				enemies.splice(j, 1);
				break;
			}
		}
		// Destroy bullets if they are behind the player
		if (bullet.x < player.x) {
			bullet.destroy();
			bullets.splice(i, 1);
		}
	}
};
game.down = function (x, y, obj) {
	var bullet = game.addChild(new Bullet());
	bullet.x = player.x;
	bullet.y = player.y;
	bullets.push(bullet);
};
game.move = function (x, y, obj) {
	player.y = y;
};

===================================================================
--- original.js
+++ change.js
@@ -38,9 +38,13 @@
 		// Scale horizontally by 1.2
 		scaleY: 3 // Scale vertically by 1.2
 	});
 	self.update = function () {
-		// Ground does not move
+		// Ground moves from right to left
+		self.x -= 5;
+		if (self.x + self.width < 0) {
+			self.x = 2048;
+		}
 	};
 });
 var Player = Container.expand(function () {
 	var self = Container.call(this);
@@ -94,9 +98,8 @@
 var bullets = [];
 game.update = function () {
 	background1.x -= 5;
 	background2.x -= 5;
-	ground.x -= 5; // Move the ground asset left side towards the player along with the game movement
 	if (background1.x <= -1024) {
 		background1.x = background2.x + 2048;
 	}
 	if (background2.x <= -1024) {