/**** 
* Classes
****/ 
// Bullet class
var Bullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletSprite = self.attachAsset('bullet', {
		anchorX: 0.5,
		anchorY: 0.5,
		flipY: 1 // flip vertically
	});
	// Target coordinates for the bullet
	self.targetX = null;
	self.targetY = null;
	self.speed = 48; // pixels per frame, positive value
	self.dirX = 0;
	self.dirY = -1;
	self.setTarget = function (tx, ty) {
		// Calculate direction vector
		var dx = tx - self.x;
		var dy = ty - self.y;
		var len = Math.sqrt(dx * dx + dy * dy);
		if (len > 0) {
			self.dirX = dx / len;
			self.dirY = dy / len;
		} else {
			self.dirX = 0;
			self.dirY = -1;
		}
		self.targetX = tx;
		self.targetY = ty;
	};
	self.update = function () {
		// Store lastX/lastY for event triggers
		if (typeof self.lastX === "undefined") self.lastX = self.x;
		if (typeof self.lastY === "undefined") self.lastY = self.y;
		// Move in direction
		self.x += self.dirX * self.speed;
		self.y += self.dirY * self.speed;
		// Rotate bullet sprite to face movement direction
		if (self.dirX !== 0 || self.dirY !== 0) {
			// atan2 returns angle in radians, 0 is to the right, so subtract Math.PI/2 to make 0 point up
			bulletSprite.rotation = Math.atan2(self.dirY, self.dirX) - Math.PI / 2;
		}
		// Update lastX/lastY for next frame
		self.lastX = self.x;
		self.lastY = self.y;
	};
	return self;
});
// Enemy class
var Enemy = Container.expand(function () {
	var self = Container.call(this);
	var enemySprite = self.attachAsset('enemy', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.radius = enemySprite.width * 0.5;
	self.speed = (5 + Math.random() * 3) * 0.5; // slightly faster zombies
	self.update = function () {
		// Move toward player
		if (typeof self.lastX === "undefined") self.lastX = self.x;
		if (typeof self.lastY === "undefined") self.lastY = self.y;
		if (player) {
			var dx = player.x - self.x;
			var dy = player.y - self.y;
			var len = Math.sqrt(dx * dx + dy * dy);
			if (len > 0) {
				self.x += dx / len * self.speed;
				self.y += dy / len * self.speed;
			} else {
				self.y += self.speed;
			}
		} else {
			self.y += self.speed;
		}
		// Update lastX/lastY for event triggers
		self.lastX = self.x;
		self.lastY = self.y;
	};
	return self;
});
// FastZombie class
var FastZombie = Container.expand(function () {
	var self = Container.call(this);
	var fastZombieSprite = self.attachAsset('FastZombie', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.radius = fastZombieSprite.width * 0.5;
	self.speed = (10 + Math.random() * 4) * 0.4; // much faster than normal zombies, but slowed down
	self.update = function () {
		// Move toward player
		if (typeof self.lastX === "undefined") self.lastX = self.x;
		if (typeof self.lastY === "undefined") self.lastY = self.y;
		if (player) {
			var dx = player.x - self.x;
			var dy = player.y - self.y;
			var len = Math.sqrt(dx * dx + dy * dy);
			if (len > 0) {
				self.x += dx / len * self.speed;
				self.y += dy / len * self.speed;
			} else {
				self.y += self.speed;
			}
		} else {
			self.y += self.speed;
		}
		// Update lastX/lastY for event triggers
		self.lastX = self.x;
		self.lastY = self.y;
	};
	return self;
});
// Obstacle class
var Obstacle = Container.expand(function () {
	var self = Container.call(this);
	var obsSprite = self.attachAsset('obstacle', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.width = obsSprite.width;
	self.height = obsSprite.height;
	self.speed = 12 + Math.random() * 8;
	self.update = function () {
		self.y += self.speed;
	};
	return self;
});
// Player class
var Player = Container.expand(function () {
	var self = Container.call(this);
	var playerSprite = self.attachAsset('player', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.radius = playerSprite.width * 0.5;
	self.lives = 1;
	self.invincible = false;
	self.invincibleTicks = 0;
	self.shootCooldown = 0;
	self.update = function () {
		if (self.invincible) {
			self.invincibleTicks--;
			if (self.invincibleTicks <= 0) {
				self.invincible = false;
				playerSprite.alpha = 1;
			} else {
				// Flicker effect
				playerSprite.alpha = LK.ticks % 10 < 5 ? 0.4 : 1;
			}
		}
		if (self.shootCooldown > 0) self.shootCooldown--;
	};
	// Called when player is hit
	self.hit = function () {
		if (self.invincible) return;
		self.lives--;
		self.invincible = true;
		self.invincibleTicks = 90; // 1.5 seconds
		playerSprite.alpha = 0.4;
		LK.effects.flashObject(self, 0xff0000, 500);
		LK.getSound('hit').play();
	};
	// Called when player picks up a powerup
	self.powerup = function () {
		self.invincible = true;
		self.invincibleTicks = 180; // 3 seconds
		playerSprite.alpha = 0.4;
		LK.getSound('powerup').play();
	};
	return self;
});

/**** 
* Initialize Game
****/ 
var game = new LK.Game({
	backgroundColor: 0x181818
});

/**** 
* Game Code
****/ 
// Game state variables
// Player character: blue box
// Enemy: red ellipse
// Obstacle: orange box
// Bullet: yellow box
// Powerup: green ellipse
// Sound effects
// Music
var player;
var bullets = [];
var enemies = [];
// Removed obstacles array as obstacles are deleted from the game
var dragNode = null;
var lastTouch = {
	x: 0,
	y: 0
};
var scoreTxt, livesTxt;
var spawnTick = 0;
var difficulty = 1;
var gameOver = false;
// UI
scoreTxt = new Text2('0', {
	size: 120,
	fill: "#fff"
});
scoreTxt.anchor.set(0.5, 0);
LK.gui.top.addChild(scoreTxt);
livesTxt = new Text2('♥♥♥', {
	size: 90,
	fill: 0xFF5252
});
livesTxt.anchor.set(1, 0);
LK.gui.topRight.addChild(livesTxt);
// Start music
LK.playMusic('music');
// Create player
player = new Player();
player.x = 2048 / 2;
player.y = 2732 / 2;
game.addChild(player);
// Helper: update lives display
function updateLives() {
	var s = '';
	for (var i = 0; i < player.lives; i++) s += '♥';
	livesTxt.setText(s);
}
// Helper: spawn enemy
function spawnEnemy() {
	var e = new Enemy();
	// Randomly pick a spawn edge: 0=top, 1=bottom, 2=left, 3=right
	var edge = Math.floor(Math.random() * 4);
	if (edge === 0) {
		// top
		e.x = 200 + Math.random() * (2048 - 400);
		e.y = -100;
	} else if (edge === 1) {
		// bottom
		e.x = 200 + Math.random() * (2048 - 400);
		e.y = 2732 + 100;
	} else if (edge === 2) {
		// left
		e.x = -100;
		e.y = 200 + Math.random() * (2732 - 400);
	} else {
		// right
		e.x = 2048 + 100;
		e.y = 200 + Math.random() * (2732 - 400);
	}
	enemies.push(e);
	game.addChild(e);
}
// Removed spawnObstacle function as obstacles are deleted from the game
// Powerup spawn helper removed as per requirements
// Touch controls: drag player
game.down = function (x, y, obj) {
	// Don't allow drag from top left 100x100
	if (x < 100 && y < 100) return;
	if (player && !gameOver) {
		dragNode = player;
		lastTouch.x = x;
		lastTouch.y = y;
	}
};
game.move = function (x, y, obj) {
	if (dragNode && !gameOver) {
		// Player movement disabled: do not update player.x or player.y
		lastTouch.x = x;
		lastTouch.y = y;
	}
};
game.up = function (x, y, obj) {
	dragNode = null;
};
// Tap to shoot (anywhere except top left 100x100)
game.on('down', function (x, y, obj) {
	if (x < 100 && y < 100) return;
	if (player && !gameOver && player.shootCooldown <= 0) {
		var b = new Bullet();
		b.x = player.x;
		b.y = player.y - player.radius - 20;
		b.setTarget(x, y); // Set bullet direction toward tap
		bullets.push(b);
		game.addChild(b);
		player.shootCooldown = 12; // 0.2s
		LK.getSound('shoot').play();
	}
});
// Main game loop
game.update = function () {
	if (gameOver) return;
	// Increase difficulty over time
	// Only increase Powerup and FastZombie spawn rates, not enemy spawn rate
	var newDifficulty = 1 + Math.floor(LK.getScore() / 50) * 0.1;
	if (newDifficulty !== difficulty) {
		difficulty = newDifficulty;
	}
	// Enemy spawn rate stays constant, but we use difficulty for powerup and fastzombie rates
	// Player update
	player.update();
	// Spawn logic
	spawnTick++;
	if (spawnTick % 30 === 0) {
		// Limit total number of enemies, fastzombies, and powerups to 10
		var totalActive = enemies.length;
		var maxActive = 10;
		// Enemy spawn rate is constant, not affected by difficulty
		if (totalActive < maxActive && Math.random() < 0.5) {
			spawnEnemy();
			totalActive++;
		}
		if (totalActive < maxActive && Math.random() < 0.10) {
			spawnEnemy();
			totalActive++;
		}
		// FastZombie: 7% base chance, scales with difficulty, only after score >= 25
		// After score > 50, FastZombie spawn chance is 50%
		var fastZombieChance = 0.07 * difficulty;
		if (LK.getScore() > 50) {
			fastZombieChance = 0.5;
		}
		if (totalActive < maxActive && LK.getScore() >= 25 && Math.random() < fastZombieChance) {
			var fz = new FastZombie();
			// Randomly pick a spawn edge: 0=top, 1=bottom, 2=left, 3=right
			var edge = Math.floor(Math.random() * 4);
			if (edge === 0) {
				// top
				fz.x = 200 + Math.random() * (2048 - 400);
				fz.y = -100;
			} else if (edge === 1) {
				// bottom
				fz.x = 200 + Math.random() * (2048 - 400);
				fz.y = 2732 + 100;
			} else if (edge === 2) {
				// left
				fz.x = -100;
				fz.y = 200 + Math.random() * (2732 - 400);
			} else {
				// right
				fz.x = 2048 + 100;
				fz.y = 200 + Math.random() * (2732 - 400);
			}
			enemies.push(fz);
			game.addChild(fz);
			totalActive++;
		}
	}
	// Bulletpowerup timer logic
	// bulletpowerupActive is now permanent once collected; timer logic removed
	// Bullets
	for (var i = bullets.length - 1; i >= 0; i--) {
		var b = bullets[i];
		b.update();
		if (b.y < -60) {
			b.destroy();
			bullets.splice(i, 1);
			continue;
		}
		// Bullet hits enemy
		for (var j = enemies.length - 1; j >= 0; j--) {
			var e = enemies[j];
			if (b.intersects(e)) {
				LK.setScore(LK.getScore() + 1);
				scoreTxt.setText(LK.getScore());
				if (LK.getScore() >= 150) {
					gameOver = true;
					LK.showYouWin();
					return;
				}
				LK.getSound('enemyDown').play();
				e.destroy();
				enemies.splice(j, 1);
				b.destroy();
				bullets.splice(i, 1);
				break;
			}
		}
	}
	// Enemies
	for (var i = enemies.length - 1; i >= 0; i--) {
		var e = enemies[i];
		e.update();
		if (e.y > 2732 + 100) {
			e.destroy();
			enemies.splice(i, 1);
			continue;
		}
		// Enemy hits player
		if (e.intersects(player)) {
			if (!player.invincible) {
				player.hit();
				updateLives();
				if (player.lives <= 0) {
					gameOver = true;
					LK.effects.flashScreen(0xff0000, 1000);
					LK.showGameOver();
					return;
				}
			}
			e.destroy();
			enemies.splice(i, 1);
		}
	}
	// Obstacles removed from game
};
// Score display
scoreTxt.setText(LK.getScore());
updateLives();

===================================================================
--- original.js
+++ change.js
@@ -216,9 +216,9 @@
 });
 livesTxt.anchor.set(1, 0);
 LK.gui.topRight.addChild(livesTxt);
 // Start music
-LK.playMusic('arcadebg');
+LK.playMusic('music');
 // Create player
 player = new Player();
 player.x = 2048 / 2;
 player.y = 2732 / 2;