/**** 
* Classes
****/ 
// Bullet class
var Bullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.attachAsset('bullet', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 15;
	self.update = function () {
		self.x += self.speed;
	};
});
// Player class
var Player = Container.expand(function () {
	var self = Container.call(this);
	var playerGraphics = self.attachAsset('player', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 10;
	self.health = 100;
	self.update = function () {};
	self.takeDamage = function (amount) {
		self.health -= amount;
	};
});
// Zombie class
var Zombie = Container.expand(function (type) {
	var self = Container.call(this);
	var zombieGraphics = self.attachAsset('zombie', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.type = type;
	self.speed = 2;
	if (self.type === 'fast') {
		self.speed = 4;
	} else if (self.type === 'strong') {
		self.speed = 1;
	}
	self.update = function () {
		var dx = player.x - self.x;
		var dy = player.y - self.y;
		var magnitude = Math.sqrt(dx * dx + dy * dy);
		dx /= magnitude;
		dy /= magnitude;
		self.x += dx * self.speed;
		self.y += dy * self.speed;
	};
});

/**** 
* Initialize Game
****/ 
var game = new LK.Game({
	backgroundColor: 0x87CEEB // Sky blue background
});

/**** 
* Game Code
****/ 
var background = game.attachAsset('background', {
	anchorX: 0,
	anchorY: 0
});
// Initialize player
var player = game.addChild(new Player());
player.x = 150;
player.y = 2732 / 2;
// Initialize health bar
var healthBarBorder = LK.getAsset('healthBarBorder', {
	anchorX: 0.5,
	anchorY: 0.5
});
healthBarBorder.x = 2048 - healthBarBorder.width / 2 - 50;
healthBarBorder.y = 2732 - 50;
game.addChild(healthBarBorder);
var healthBar = LK.getAsset('healthBar', {
	anchorX: 0,
	// Align to the left side
	anchorY: 0.5
});
healthBar.x = healthBarBorder.x - healthBarBorder.width / 2; // Align to left side of border
healthBar.y = healthBarBorder.y;
game.addChild(healthBar);
// Initialize score
var score = 0;
var scoreTxt = new Text2('Score: 0', {
	size: 100,
	fill: 0xFFFFFF
});
scoreTxt.anchor.set(0.5, 0);
LK.gui.top.addChild(scoreTxt);
scoreTxt.x = 2048 / 2;
scoreTxt.y = 50;
// Bullet and zombie tracking
var bullets = [];
var zombies = [];
// Spawn zombies
function spawnZombie() {
	var type = 'normal';
	if (LK.ticks > 1200) {
		type = 'fast';
	} else if (LK.ticks > 2400) {
		type = 'strong';
	}
	var zombie = new Zombie(type);
	zombie.x = 2048;
	zombie.y = Math.random() * 2732;
	zombies.push(zombie);
	game.addChild(zombie);
}
// Shooting bullets
function shootBullet() {
	var bullet = new Bullet();
	bullet.x = player.x;
	bullet.y = player.y;
	bullets.push(bullet);
	game.addChild(bullet);
	LK.getSound('shoot').play();
}
// Update loop
game.update = function () {
	player.update();
	if (LK.ticks % 600 === 0) {
		var waveTxt = new Text2('Wave ' + LK.ticks / 600 + ' Start!', {
			size: 100,
			fill: 0xFFFFFF
		});
		waveTxt.anchor.set(0.5, 0);
		LK.gui.top.addChild(waveTxt);
		waveTxt.x = 2048 / 2;
		waveTxt.y = 2732 / 2;
		LK.setTimeout(function () {
			waveTxt.destroy();
		}, 2000);
	}
	// Update health bar width and position
	if (player.health > 0) {
		healthBar.width = player.health * 10;
	} else {
		healthBar.width = 0;
		LK.showGameOver();
	}
	// Update bullets
	for (var i = bullets.length - 1; i >= 0; i--) {
		bullets[i].update();
		if (bullets[i].x > 2048) {
			bullets[i].destroy();
			bullets.splice(i, 1);
		}
	}
	// Update zombies
	for (var j = zombies.length - 1; j >= 0; j--) {
		zombies[j].update();
		if (zombies[j].intersects(player)) {
			player.takeDamage(10);
			zombies[j].destroy();
			zombies.splice(j, 1);
			LK.getSound('zombieHit').play();
		}
	}
	// Bullet-zombie collisions
	for (var k = bullets.length - 1; k >= 0; k--) {
		for (var l = zombies.length - 1; l >= 0; l--) {
			if (bullets[k].intersects(zombies[l])) {
				score += 10;
				scoreTxt.setText('Score: ' + score);
				bullets[k].destroy();
				zombies[l].destroy();
				bullets.splice(k, 1);
				zombies.splice(l, 1);
				LK.getSound('zombieKill').play();
				break;
			}
		}
	}
	// Spawn zombies every 60 ticks
	if (LK.ticks % 60 === 0) {
		for (var i = 0; i < Math.floor(LK.ticks / 600) + 5; i++) {
			spawnZombie();
		}
	}
};
// Player controls
game.down = function (x, y, obj) {
	shootBullet();
};
game.move = function (x, y, obj) {
	player.x = x;
	player.y = y;
};

===================================================================
--- original.js
+++ change.js
@@ -27,15 +27,21 @@
 		self.health -= amount;
 	};
 });
 // Zombie class
-var Zombie = Container.expand(function () {
+var Zombie = Container.expand(function (type) {
 	var self = Container.call(this);
 	var zombieGraphics = self.attachAsset('zombie', {
 		anchorX: 0.5,
 		anchorY: 0.5
 	});
+	self.type = type;
 	self.speed = 2;
+	if (self.type === 'fast') {
+		self.speed = 4;
+	} else if (self.type === 'strong') {
+		self.speed = 1;
+	}
 	self.update = function () {
 		var dx = player.x - self.x;
 		var dy = player.y - self.y;
 		var magnitude = Math.sqrt(dx * dx + dy * dy);
@@ -94,9 +100,15 @@
 var bullets = [];
 var zombies = [];
 // Spawn zombies
 function spawnZombie() {
-	var zombie = new Zombie();
+	var type = 'normal';
+	if (LK.ticks > 1200) {
+		type = 'fast';
+	} else if (LK.ticks > 2400) {
+		type = 'strong';
+	}
+	var zombie = new Zombie(type);
 	zombie.x = 2048;
 	zombie.y = Math.random() * 2732;
 	zombies.push(zombie);
 	game.addChild(zombie);
@@ -112,8 +124,21 @@
 }
 // Update loop
 game.update = function () {
 	player.update();
+	if (LK.ticks % 600 === 0) {
+		var waveTxt = new Text2('Wave ' + LK.ticks / 600 + ' Start!', {
+			size: 100,
+			fill: 0xFFFFFF
+		});
+		waveTxt.anchor.set(0.5, 0);
+		LK.gui.top.addChild(waveTxt);
+		waveTxt.x = 2048 / 2;
+		waveTxt.y = 2732 / 2;
+		LK.setTimeout(function () {
+			waveTxt.destroy();
+		}, 2000);
+	}
 	// Update health bar width and position
 	if (player.health > 0) {
 		healthBar.width = player.health * 10;
 	} else {
@@ -154,9 +179,11 @@
 		}
 	}
 	// Spawn zombies every 60 ticks
 	if (LK.ticks % 60 === 0) {
-		spawnZombie();
+		for (var i = 0; i < Math.floor(LK.ticks / 600) + 5; i++) {
+			spawnZombie();
+		}
 	}
 };
 // Player controls
 game.down = function (x, y, obj) {