/**** 
* Classes
****/ 
// 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 = 2;
	self.move = function () {
		self.y += self.speed;
	};
});
// EnemyBullet class
var EnemyBullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.attachAsset('enemyBullet', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 5;
	self.move = function () {
		self.y += self.speed;
	};
});
// Assets will be automatically generated based on usage in the code.
// Hero class
var Hero = Container.expand(function () {
	var self = Container.call(this);
	var heroGraphics = self.attachAsset('hero', {
		anchorX: 0.5,
		anchorY: 0.5,
		scaleX: 2,
		scaleY: 2
	});
	heroGraphics.tint = 0xFF69B4;
	self.move = function (x, y) {
		self.x = x;
		self.y = y;
	};
});

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

/**** 
* Game Code
****/ 
// Global variables
var hero = new Hero();
hero.x = 1024; // Center horizontally
hero.y = 2500; // Near the bottom
var enemies = [];
var enemyBullets = [];
// Add hero to the game
game.addChild(hero);
// Touch event to move hero and shoot
game.on('down', function (obj) {
	var pos = obj.event.getLocalPosition(game);
	hero.move(pos.x, pos.y);
	hero.shoot();
});
// Game tick event
LK.on('tick', function () {
	// Move enemies and enemy bullets
	for (var j = enemies.length - 1; j >= 0; j--) {
		enemies[j].move();
		if (enemies[j].y > 2732) {
			// Enemy off-screen
			enemies[j].destroy();
			enemies.splice(j, 1);
		}
	}
	for (var k = enemyBullets.length - 1; k >= 0; k--) {
		enemyBullets[k].move();
		if (enemyBullets[k].y > 2732) {
			// Bullet off-screen
			enemyBullets[k].destroy();
			enemyBullets.splice(k, 1);
		}
		// Check collision with hero
		if (hero.intersects(enemyBullets[k])) {
			LK.effects.flashScreen(0xff0000, 1000);
			LK.showGameOver();
		}
	}
	// Spawn enemies and bullets
	if (LK.ticks % 120 == 0) {
		// Every 2 seconds
		var enemy = new Enemy();
		enemy.x = Math.random() * 2048;
		enemy.y = 0;
		game.addChild(enemy);
		enemies.push(enemy);
		var enemyBullet = new EnemyBullet();
		enemyBullet.x = enemy.x;
		enemyBullet.y = enemy.y + 50;
		game.addChild(enemyBullet);
		enemyBullets.push(enemyBullet);
	}
});

===================================================================
--- original.js
+++ change.js
@@ -39,29 +39,9 @@
 	self.move = function (x, y) {
 		self.x = x;
 		self.y = y;
 	};
-	self.shoot = function () {
-		var bullet = new HeroBullet();
-		bullet.x = self.x;
-		bullet.y = self.y - 50; // Shoot from above the hero
-		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
-	});
-	bulletGraphics.tint = 0x90EE90;
-	self.speed = -10;
-	self.move = function () {
-		self.y += self.speed;
-	};
-});
 
 /**** 
 * Initialize Game
 ****/ 
@@ -75,9 +55,8 @@
 // Global variables
 var hero = new Hero();
 hero.x = 1024; // Center horizontally
 hero.y = 2500; // Near the bottom
-var heroBullets = [];
 var enemies = [];
 var enemyBullets = [];
 // Add hero to the game
 game.addChild(hero);
@@ -88,17 +67,8 @@
 	hero.shoot();
 });
 // Game tick event
 LK.on('tick', function () {
-	// Move hero bullets
-	for (var i = heroBullets.length - 1; i >= 0; i--) {
-		heroBullets[i].move();
-		if (heroBullets[i].y < 0) {
-			// Bullet off-screen
-			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].y > 2732) {
@@ -118,20 +88,8 @@
 		if (hero.intersects(enemyBullets[k])) {
 			LK.effects.flashScreen(0xff0000, 1000);
 			LK.showGameOver();
 		}
-		// Check collision between hero bullets and enemies
-		for (var i = heroBullets.length - 1; i >= 0; i--) {
-			for (var j = enemies.length - 1; j >= 0; j--) {
-				if (heroBullets[i].intersects(enemies[j])) {
-					enemies[j].destroy();
-					enemies.splice(j, 1);
-					heroBullets[i].destroy();
-					heroBullets.splice(i, 1);
-					break;
-				}
-			}
-		}
 	}
 	// Spawn enemies and bullets
 	if (LK.ticks % 120 == 0) {
 		// Every 2 seconds