var Hero = Container.expand(function () {
	var self = Container.call(this);
	var heroGraphics = self.createAsset('hero', 'Hero Plane', .5, .5);
	self.speed = 5;
	self.move = function () {};
	self.fire = function () {};
});
var Enemy = Container.expand(function () {
	var self = Container.call(this);
	var enemyGraphics = self.createAsset('enemy', 'Enemy Plane', .5, .5);
	self.speed = -3;
	self.move = function () {
		self.y += self.speed;
	};
	self.fire = function () {
		var bullet = new EnemyBullet();
		bullet.x = self.x;
		bullet.y = self.y;
		bullet.move = function () {
			bullet.y += bullet.speed;
		};
		enemyBullets.push(bullet);
		self.parent.addChild(bullet);
	};
});
var HeroBullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.createAsset('heroBullet', 'Hero Bullet', .5, .5);
	self.speed = 10;
	self.move = function () {
		self.y -= self.speed;
	};
});
var EnemyBullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.createAsset('enemyBullet', 'Enemy Bullet', .5, .5);
	self.speed = -7;
	self.move = function () {
		self.y += self.speed;
	};
});
var Game = Container.expand(function () {
	var self = Container.call(this);
	var bg = self.createAsset('background', 'Background Image', 0, 0);
	bg.width = 2048;
	bg.height = 2732;
	var bg2 = self.createAsset('background', 'Background Image', 0, 0);
	bg2.width = 2048;
	bg2.height = 2732;
	bg2.y = -2732;
	var hero = self.addChild(new Hero());
	var enemies = [];
	var heroBullets = [];
	var enemyBullets = [];
	hero.x = 2048 / 2;
	hero.y = 2732 - 200;
	var spawnEnemy = function () {
		var enemy = new Enemy();
		enemy.x = Math.random() * 2048;
		enemy.y = 0;
		enemies.push(enemy);
		self.addChild(enemy);
	};
	var spawnHeroBullet = function () {
		var bullet = new HeroBullet();
		bullet.x = hero.x;
		bullet.y = hero.y;
		bullet.move = function () {
			bullet.y -= bullet.speed;
		};
		heroBullets.push(bullet);
		self.addChild(bullet);
	};
	var spawnEnemyBullet = function () {};
	var checkCollision = function () {};
	var gameOver = function () {};
	LK.on('tick', function () {
		bg.y += 2;
		bg2.y += 2;
		if (bg.y >= 2732) bg.y = -2732;
		if (bg2.y >= 2732) bg2.y = -2732;
		hero.move();
		enemies.forEach(function (enemy, index) {
			enemy.move();
			if (LK.ticks % 60 === 0) {
				enemy.fire();
			}
			if (enemy.y > 2732) {
				enemy.destroy();
				enemies.splice(index, 1);
			}
		});
		heroBullets.forEach(function (bullet, index) {
			bullet.move();
			if (bullet.y < 0) {
				bullet.destroy();
				heroBullets.splice(index, 1);
			}
		});
		enemyBullets.forEach(function (bullet) {
			bullet.move();
		});
		checkCollision();
	});
	LK.on('tick', function () {
		if (LK.ticks % 30 === 0) {
			spawnHeroBullet();
		}
	});
	var dragHero = null;
	stage.on('down', function (obj) {
		dragHero = hero;
	});
	stage.on('move', function (obj) {
		if (dragHero) {
			var pos = obj.event.getLocalPosition(self);
			dragHero.x = pos.x;
			dragHero.y = pos.y;
		}
	});
	stage.on('up', function (obj) {
		dragHero = null;
	});
});

===================================================================
--- original.js
+++ change.js
@@ -1,11 +1,9 @@
 var Hero = Container.expand(function () {
 	var self = Container.call(this);
 	var heroGraphics = self.createAsset('hero', 'Hero Plane', .5, .5);
 	self.speed = 5;
-	self.move = function () {
-		self.y -= self.speed;
-	};
+	self.move = function () {};
 	self.fire = function () {};
 });
 var Enemy = Container.expand(function () {
 	var self = Container.call(this);