===================================================================
--- original.js
+++ change.js
@@ -1,19 +1,7 @@
 /**** 
 * 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', {
@@ -55,10 +43,8 @@
 // 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) {
@@ -68,40 +54,6 @@
 });
 // 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);
-	}
 });
\ No newline at end of file