/**** 
* Classes
****/
var Hero = Container.expand(function () {
	var self = Container.call(this);
	var heroGraphics = self.attachAsset('hero', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	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 - self.height / 2;
		game.addChild(bullet);
		return bullet;
	};
});
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;
	};
	self.shoot = function () {
		var bullet = new EnemyBullet();
		bullet.x = self.x;
		bullet.y = self.y + self.height / 2;
		game.addChild(bullet);
		return bullet;
	};
});
var HeroBullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.attachAsset('heroBullet', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = -5;
	self.move = function () {
		self.y += self.speed;
	};
});
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;
	};
});

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

/**** 
* Game Code
****/
var hero = game.addChild(new Hero());
hero.x = 2048 / 2;
hero.y = 2732 - 100;
var enemies = [];
var heroBullets = [];
var enemyBullets = [];
var score = 0;
var scoreTxt = new Text2(score.toString(), {
	size: 150,
	fill: "#ffffff"
});
scoreTxt.anchor.set(0.5, 0);
LK.gui.top.addChild(scoreTxt);
game.on('down', function (obj) {
	var pos = obj.event.getLocalPosition(game);
	hero.move(pos.x, pos.y);
});
LK.on('tick', function () {
	// Move hero bullets
	for (var i = heroBullets.length - 1; i >= 0; i--) {
		heroBullets[i].move();
		if (heroBullets[i].y < 0) {
			heroBullets[i].destroy();
			heroBullets.splice(i, 1);
		}
	}
	// Move enemies and make them shoot
	for (var j = enemies.length - 1; j >= 0; j--) {
		enemies[j].move();
		if (LK.ticks % 120 == 0) {
			enemyBullets.push(enemies[j].shoot());
		}
		if (enemies[j].y > 2732) {
			enemies[j].destroy();
			enemies.splice(j, 1);
		}
	}
	// Check for collisions
	for (var k = heroBullets.length - 1; k >= 0; k--) {
		for (var l = enemies.length - 1; l >= 0; l--) {
			if (heroBullets[k].intersects(enemies[l])) {
				heroBullets[k].destroy();
				heroBullets.splice(k, 1);
				enemies[l].destroy();
				enemies.splice(l, 1);
				score += 10;
				scoreTxt.setText(score.toString());
				break;
			}
		}
	}
	// Spawn enemies
	if (LK.ticks % 120 == 0) {
		var enemy = new Enemy();
		enemy.x = Math.random() * (2048 - enemy.width) + enemy.width / 2;
		enemy.y = -enemy.height / 2;
		enemies.push(enemy);
		game.addChild(enemy);
	}
	// Hero shoot
	if (LK.ticks % 30 == 0) {
		heroBullets.push(hero.shoot());
	}
});

===================================================================
--- original.js
+++ change.js
@@ -28,8 +28,15 @@
 	self.speed = 2;
 	self.move = function () {
 		self.y += self.speed;
 	};
+	self.shoot = function () {
+		var bullet = new EnemyBullet();
+		bullet.x = self.x;
+		bullet.y = self.y + self.height / 2;
+		game.addChild(bullet);
+		return bullet;
+	};
 });
 var HeroBullet = Container.expand(function () {
 	var self = Container.call(this);
 	var bulletGraphics = self.attachAsset('heroBullet', {
@@ -40,8 +47,19 @@
 	self.move = function () {
 		self.y += self.speed;
 	};
 });
+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;
+	};
+});
 
 /**** 
 * Initialize Game
 ****/
@@ -56,8 +74,9 @@
 hero.x = 2048 / 2;
 hero.y = 2732 - 100;
 var enemies = [];
 var heroBullets = [];
+var enemyBullets = [];
 var score = 0;
 var scoreTxt = new Text2(score.toString(), {
 	size: 150,
 	fill: "#ffffff"
@@ -76,11 +95,14 @@
 			heroBullets[i].destroy();
 			heroBullets.splice(i, 1);
 		}
 	}
-	// Move enemies
+	// Move enemies and make them shoot
 	for (var j = enemies.length - 1; j >= 0; j--) {
 		enemies[j].move();
+		if (LK.ticks % 120 == 0) {
+			enemyBullets.push(enemies[j].shoot());
+		}
 		if (enemies[j].y > 2732) {
 			enemies[j].destroy();
 			enemies.splice(j, 1);
 		}