var Obstacle = Container.expand(function () {
	var self = Container.call(this);
	var obstacleGraphics = self.addChild(XS.getAsset('obstacle', 'Obstacle', .5, 1));
	obstacleGraphics.y += 50;
});
var ExitDoor = Container.expand(function () {
	var self = Container.call(this);
	var backgroundElement = self.addChild(XS.getAsset('backgroundElement1', 'Background Element 1', .5, .5));
	backgroundElement.y -= 760;
	var backgroundElement2 = self.addChild(XS.getAsset('backgroundElement2', 'Background Element 2', .5, .5));
	backgroundElement2.y -= 760;
	backgroundElement2.blendMode = 1;
	var doorGraphics = self.addChild(XS.getAsset('exitDoor', 'Exit Door', .5, 1));
	self.rotationSpeed1 = 0.005 * 0.25;
	self.rotationSpeed2 = 0.007 * 0.25;
	self.rotate = function () {
		backgroundElement.rotation += self.rotationSpeed1;
		backgroundElement2.rotation -= self.rotationSpeed2;
	};
});
var EnemySpawnIndicator = Container.expand(function () {
	var self = Container.call(this);
	var spawnIndicatorGraphics = self.addChild(XS.getAsset('spawnIndicator', 'Enemy Spawn Indicator', .5, .5));
	spawnIndicatorGraphics.alpha = 0.5;
});
var ExplosionParticle = Container.expand(function () {
	var self = Container.call(this);
	var particleGraphics = self.addChild(XS.getAsset('particle', 'Explosion Particle', .5, .5));
	self.dx = (Math.random() - 0.5) * 10;
	self.dy = (Math.random() - 0.5) * 7;
	self.move = function () {
		self.setPosition(self.x + self.dx, self.y + self.dy);
		self.alpha -= 0.02;
		particleGraphics.scale.set(particleGraphics.scale.x * 0.98, particleGraphics.scale.y * 0.98);
		self.dx *= 0.98;
		self.dy *= 0.98;
		if (self.alpha <= 0) {
			self.destroy();
		}
	};
});
var HealthBar = Container.expand(function () {
	var self = Container.call(this);
	var healthBarGraphics = XS.getAsset('healthBar', 'Health Bar', .5, 1);
	self.addChild(healthBarGraphics);
	self.setTint = function (tint) {
		healthBarGraphics.tint = tint;
	};
	self.setTint(0x00FF00);
	self.updateHealth = function (health) {
		self.scale.set(health / 100, 1);
	};
});
var TargetIndicator = Container.expand(function () {
	var self = Container.call(this);
	var targetGraphics = XS.getAsset('target', 'Target Indicator', .5, .5);
	targetGraphics.alpha = 0.5;
	targetGraphics.y -= 30;
	self.addChild(targetGraphics);
});
var Player = Container.expand(function () {
	var self = Container.call(this);
	self.health = 100;
	self.findNearestEnemy = function (enemies) {
		var nearestEnemy = null;
		var nearestDistance = Infinity;
		for (var i = 0; i < enemies.length; i++) {
			var dx = enemies[i].x - self.x;
			var dy = enemies[i].y - self.y;
			var distance = Math.sqrt(dx * dx + dy * dy);
			if (distance < nearestDistance && !self.parent.lineIntersectsObstacle(self.x, self.y, enemies[i].x, enemies[i].y)) {
				nearestDistance = distance;
				nearestEnemy = enemies[i];
			}
		}
		return nearestEnemy;
	};
	var playerShadow = self.addChild(XS.getAsset('playerShadow', 'Player shadow', .5, .8));
	playerShadow.alpha = 0.3;
	self.addChild(XS.getAsset('player', 'Player character', .5, 1));
	var healthBar = new HealthBar();
	self.addChild(healthBar).y = -self.children[1].height;
	self.healthBar = healthBar;
	self.targetX = 2048 / 2;
	self.targetY = 2732 / 2;
	self.speed = 5;
	self.lastShot = 0;
	self.move = function (obstacles) {
		var dx = self.targetX - self.x;
		var dy = self.targetY - self.y;
		var distance = Math.sqrt(dx * dx + dy * dy);
		if (distance > self.speed) {
			self.setPosition(self.x + dx / distance * self.speed, self.y + dy / distance * self.speed);
			for (var i = 0; i < obstacles.length; i++) {
				var dx = obstacles[i].x - self.x;
				var dy = obstacles[i].y - self.y;
				var distance = Math.sqrt(dx * dx + dy * dy);
				if (distance < obstacles[i].width / 2) {
					self.x -= dx / distance * 10;
					self.y -= dy / distance * 10;
				}
			}
			self.healthBar.updateHealth(self.health);
			return true;
		}
		self.healthBar.updateHealth(self.health);
		return false;
	};
	self.setTarget = function (x, y) {
		self.targetX = x;
		self.targetY = y;
	};
	self.shoot = function (enemies) {
		var nearestEnemy = self.findNearestEnemy(enemies);
		if (nearestEnemy) {
			var bullet = new PlayerBullet();
			bullet.x = self.x;
			bullet.y = self.y;
			var dx = nearestEnemy.x - self.x;
			var dy = nearestEnemy.y - self.y;
			var distance = Math.sqrt(dx * dx + dy * dy);
			bullet.dx = dx / distance;
			bullet.dy = dy / distance;
			return bullet;
		}
		return null;
	};
});
var Enemy = Container.expand(function () {
	var self = Container.call(this);
	self.throwProjectile = function (player) {
		if (!self.parent.lineIntersectsObstacle(self.x, self.y, player.x, player.y)) {
			var dx = player.x - self.x;
			var dy = player.y - self.y;
			var distance = Math.sqrt(dx * dx + dy * dy);
			var projectile = new EnemyBullet();
			projectile.x = self.x;
			projectile.y = self.y;
			projectile.dx = dx / distance;
			projectile.dy = dy / distance;
			return projectile;
		}
		return null;
	};
	self.moveTowardsPlayer = function (player) {
		if (!self.parent.lineIntersectsObstacle(self.x, self.y, player.x, player.y)) {
			var dx = player.x - self.x;
			var dy = player.y - self.y;
			var distance = Math.sqrt(dx * dx + dy * dy);
			if (distance > 800) {
				self.dx += dx / distance * 0.3;
				self.dy += dy / distance * 0.3;
			}
		}
	};
	;
	self.alpha = 0;
	self.lastProjectile = 0;
	self.dx = 0;
	self.dy = 0;
	self.fadeRedTint = function () {
		if (self.fadeOutRedTint > 0) {
			enemyGraphics.tint = 0xff0000 + (0xffffff - 0xff0000) * (10 - self.fadeOutRedTint) / 10;
			if (--self.fadeOutRedTint <= 0) {
				enemyGraphics.tint = 0xFFFFFF;
			}
		}
	};
	self.health = 100;
	self.animateIn = function () {
		self.fadeInTicks = 50;
	};
	var enemyShadow = self.addChild(XS.getAsset('enemyShadow', 'Enemy shadow', .5, .8));
	enemyShadow.alpha = 0.3;
	var enemyGraphics = self.addChild(XS.getAsset('enemy', 'Enemy character', .5, 1));
	var healthBar = new HealthBar();
	healthBar.setTint(0xFF0000);
	healthBar.y = -enemyGraphics.height;
	self.addChild(healthBar);
	self.healthBar = healthBar;
	self.healthBar.updateHealth(self.health);
	self.move = function (obstacles, player) {
		self.fadeRedTint();
		if (self.fadeInTicks > 0) {
			self.alpha += 0.02;
			self.fadeInTicks--;
		} else {
			self.moveTowardsPlayer(player);
		}
		self.setPosition(self.x + self.dx, self.y + self.dy);
		self.dx *= 0.80;
		self.dy *= 0.80;
		if (self.x < 150 || self.x > 2048 - 150 || self.y < 700 || self.y > 2732 - 150) {
			self.x = Math.max(Math.min(self.x, 2048 - 150), 150);
			self.y = Math.max(Math.min(self.y, 2732 - 150), 700);
		}
		for (var i = 0; i < obstacles.length; i++) {
			var dx = obstacles[i].x - self.x;
			var dy = obstacles[i].y - self.y;
			var distance = Math.sqrt(dx * dx + dy * dy);
			if (distance < obstacles[i].width / 2) {
				self.x -= dx / distance * 10;
				self.y -= dy / distance * 10;
			}
		}
	};
	self.flashRed = function () {
		self.children[0].tint = 0xFF0000;
		self.fadeOutRedTint = 10;
	};
});
var PlayerBullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.addChild(XS.getAsset('bullet', 'Bullet', .5, .5));
	bulletGraphics.y -= 150;
	bulletGraphics.blendMode = 1;
	self.dx = 0;
	self.dy = 0;
	self.move = function () {
		self.dx *= 1.02;
		self.dy *= 1.02;
		self.setPosition(self.x + self.dx * 4, self.y + self.dy * 4);
		if (self.x < 150 || self.x > 2048 - 150 || self.y < 700 || self.y > 2732 - 150) {
			return true;
		}
		return false;
	};
});
var EnemyBullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.addChild(XS.getAsset('bullet', 'Bullet', .5, .5));
	bulletGraphics.y -= 150;
	bulletGraphics.blendMode = 1;
	self.dx = 0;
	self.dy = 0;
	self.move = function () {
		self.dx *= 1.02;
		self.dy *= 1.02;
		self.setPosition(self.x + self.dx * 4, self.y + self.dy * 4);
		if (self.x < 150 || self.x > 2048 - 150 || self.y < 700 || self.y > 2732 - 150) {
			return true;
		}
		return false;
	};
});
var Background = Container.expand(function () {
	var self = Container.call(this);
	var backgroundGraphics = XS.getAsset('background', 'Background', .5, .5);
	backgroundGraphics.x = 2048 / 2;
	backgroundGraphics.y = 2732 / 2 + 300;
	self.addChild(backgroundGraphics);
	self.exitDoor = self.addChildAt(new ExitDoor(), 1);
	self.exitDoor.x = 2048 / 2;
	self.exitDoor.y = 2732 / 2 - 670 + 400;
	self.exitDoor.visible = false;
});
var Game = Container.expand(function () {
	var self = Container.call(this);
	self.lineIntersectsObstacle = function (x1, y1, x2, y2) {
		for (var i = 0; i < obstacles.length; i++) {
			var dx = obstacles[i].x - x1;
			var dy = obstacles[i].y - y1;
			var distance = Math.sqrt(dx * dx + dy * dy);
			var radius = obstacles[i].width * 0.7 / 2;
			if (distance < radius) {
				return true;
			}
			var t = ((x2 - x1) * (obstacles[i].x - x1) + (y2 - y1) * (obstacles[i].y - y1)) / (Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));
			t = Math.max(0, Math.min(1, t));
			var nearestX = x1 + t * (x2 - x1);
			var nearestY = y1 + t * (y2 - y1);
			dx = obstacles[i].x - nearestX;
			dy = obstacles[i].y - nearestY;
			distance = Math.sqrt(dx * dx + dy * dy);
			if (distance <= radius) {
				return true;
			}
		}
		return false;
	};
	self.allEnemiesKilled = false;
	self.setPlayerTarget = function (x, y) {
		x = Math.max(Math.min(x, 2048 - 150), 150);
		y = Math.max(Math.min(y, 2732 - 150), 700);
		player.setTarget(x, y);
		targetIndicator.setPosition(x, y);
		targetIndicator.visible = true;
	};
	self.checkEnemies = function () {
		if (!self.allEnemiesKilled && enemies.length === 0 && spawnIndicators.length === 0) {
			background.exitDoor.visible = true;
			self.allEnemiesKilled = true;
			XS.effects.flashScreen(0xFFFFFF, 1000);
			self.setPlayerTarget(background.exitDoor.x, background.exitDoor.y - 300);
		}
	};
	self.rotateBackground = function () {
		background.children[1].rotate();
	};
	self.particleMove = function () {
		for (var i = particles.length - 1; i >= 0; i--) {
			if (particles[i].alpha <= 0) {
				particles[i].destroy();
				particles.splice(i, 1);
			} else {
				particles[i].move();
			}
		}
	};
	self.bulletMove = function () {
		for (var i = bullets.length - 1; i >= 0; i--) {
			if (bullets[i] && bullets[i].move()) {
				self.createExplosion(bullets[i].x, bullets[i].y);
				bullets[i].destroy();
				bullets.splice(i, 1);
			} else {
				bullets[i].move();
				for (var j = 0; j < enemies.length; j++) {
					if (bullets[i].intersects(enemies[j])) {
						enemies[j].health -= 10;
						enemies[j].healthBar.updateHealth(enemies[j].health);
						enemies[j].flashRed();
						if (enemies[j].health <= 0) {
							enemies[j].destroy();
							enemies.splice(j, 1);
						} else {
							var angle = Math.atan2(bullets[i].dy, bullets[i].dx);
							enemies[j].x += Math.cos(angle) * 15;
							enemies[j].y += Math.sin(angle) * 15;
							enemies[j].dx = Math.cos(angle) * 10;
							enemies[j].dy = Math.sin(angle) * 10;
						}
						self.createExplosion(bullets[i].x, bullets[i].y);
						bullets[i].destroy();
						bullets.splice(i, 1);
						break;
					}
				}
			}
		}
	};
	self.enemyMove = function () {
		for (var i = 0; i < enemies.length; i++) {
			enemies[i].move(obstacles, player);
			for (var j = i + 1; j < enemies.length; j++) {
				var dx = enemies[j].x - enemies[i].x;
				var dy = enemies[j].y - enemies[i].y;
				var distance = Math.sqrt(dx * dx + dy * dy);
				if (distance < enemies[i].width) {
					enemies[i].x -= dx / distance;
					enemies[i].y -= dy / distance;
					enemies[j].x += dx / distance;
					enemies[j].y += dy / distance;
				}
			}
		}
	};
	self.playerMove = function (obstacles) {
		player.move(obstacles);
		var dx = player.targetX - player.x;
		var dy = player.targetY - player.y;
		var distance = Math.sqrt(dx * dx + dy * dy);
		if (distance < player.speed && XS.ticks - player.lastShot >= 60 && enemies.length > 0) {
			player.lastShot = XS.ticks;
			var bullet = player.shoot(enemies);
			if (bullet) {
				bullets.push(bullet);
				self.addChild(bullet);
			}
		}
		if (distance < player.speed) {
			targetIndicator.visible = false;
			if (self.allEnemiesKilled) {
				self.spawnNextWave();
			}
		}
	};
	var spawnIndicators = [];
	self.isTooClose = function (x, y) {
		for (var i = 0; i < spawnIndicators.length; i++) {
			var dx = spawnIndicators[i].x - x;
			var dy = spawnIndicators[i].y - y;
			var distance = Math.sqrt(dx * dx + dy * dy);
			if (distance < 200) {
				return true;
			}
		}
		return false;
	};
	self.spawnEnemies = function (count) {
		for (var i = 0; i < count; i++) {
			var x, y;
			do {
				x = Math.random() * (2048 - 300) + 150;
				y = Math.random() * (2732 - 850) + 700;
			} while (self.isTooClose(x, y) || self.lineIntersectsObstacle(x, y, x, y));
			var spawnIndicator = self.addChild(new EnemySpawnIndicator());
			spawnIndicator.setPosition(x, y);
			spawnIndicators.push(spawnIndicator);
			(function (spawnIndicator) {
				XS.setTimeout(function () {
					var enemy = self.addChild(new Enemy());
					enemy.setPosition(spawnIndicator.x, spawnIndicator.y);
					enemies.push(enemy);
					spawnIndicator.destroy();
					enemy.animateIn();
					var index = spawnIndicators.indexOf(spawnIndicator);
					if (index > -1) {
						spawnIndicators.splice(index, 1);
					}
				}, 3000);
			})(spawnIndicator);
		}
	};
	self.createExplosion = function (x, y) {
		for (var j = 0; j < 10; j++) {
			var particle = new ExplosionParticle();
			particle.setPosition(x, y);
			particle.dx = (Math.random() - 0.5) * 10;
			particle.dy = (Math.random() - 0.5) * 7;
			self.addChild(particle);
			particles.push(particle);
		}
	};
	var particles = [];
	self.sortGameObjects = function () {
		self.children.sort(function (a, b) {
			return a.y < b.y ? -1 : 1;
		});
		self.setChildIndex(targetIndicator, 1);
	};
	var background = self.addChild(new Background());
	var player = self.addChild(new Player());
	player.setPosition(2048 / 2, 2732 - player.height);
	player.setTarget(player.x, player.y);
	var targetIndicator = self.addChild(new TargetIndicator());
	targetIndicator.setPosition(player.x, player.y);
	var obstacles = [];
	var enemies = [];
	self.spawnEnemies(5);
	var obstacleSpacing = 2048 / 3;
	for (var i = 0; i < 2; i++) {
		var obstacle = self.addChild(new Obstacle());
		obstacle.setPosition(obstacleSpacing * (i + 1), 2732 / 2 + 500);
		obstacles.push(obstacle);
	}
	var bullets = [];
	XS.on('tick', function () {
		self.playerMove(obstacles);
		self.bulletMove();
		self.enemyMove();
		for (var i = 0; i < enemies.length; i++) {
			if (XS.ticks - enemies[i].lastProjectile >= 60) {
				enemies[i].lastProjectile = XS.ticks;
				var projectile = enemies[i].throwProjectile(player);
				if (projectile) {
					bullets.push(projectile);
					self.addChild(projectile);
				}
			}
		}
		self.particleMove();
		self.rotateBackground();
		self.sortGameObjects();
		self.checkEnemies();
	});
	self.spawnNextWave = function () {
		player.setPosition(2048 / 2, 2732 - player.height);
		player.setTarget(player.x, player.y);
		background.exitDoor.visible = false;
		self.allEnemiesKilled = false;
		self.spawnEnemies(5);
		XS.effects.flashScreen(0x000000, 1000);
	};
	stage.on('down', function (obj) {
		if (!self.allEnemiesKilled) {
			var pos = obj.event.getLocalPosition(self);
			self.setPlayerTarget(pos.x, pos.y);
		}
	});
});

===================================================================
--- original.js
+++ change.js
@@ -112,9 +112,9 @@
 	};
 	self.shoot = function (enemies) {
 		var nearestEnemy = self.findNearestEnemy(enemies);
 		if (nearestEnemy) {
-			var bullet = new Bullet();
+			var bullet = new PlayerBullet();
 			bullet.x = self.x;
 			bullet.y = self.y;
 			var dx = nearestEnemy.x - self.x;
 			var dy = nearestEnemy.y - self.y;
@@ -132,9 +132,9 @@
 		if (!self.parent.lineIntersectsObstacle(self.x, self.y, player.x, player.y)) {
 			var dx = player.x - self.x;
 			var dy = player.y - self.y;
 			var distance = Math.sqrt(dx * dx + dy * dy);
-			var projectile = new Bullet();
+			var projectile = new EnemyBullet();
 			projectile.x = self.x;
 			projectile.y = self.y;
 			projectile.dx = dx / distance;
 			projectile.dy = dy / distance;
@@ -208,11 +208,10 @@
 		self.children[0].tint = 0xFF0000;
 		self.fadeOutRedTint = 10;
 	};
 });
-var Bullet = Container.expand(function (type) {
+var PlayerBullet = Container.expand(function () {
 	var self = Container.call(this);
-	self.type = type;
 	var bulletGraphics = self.addChild(XS.getAsset('bullet', 'Bullet', .5, .5));
 	bulletGraphics.y -= 150;
 	bulletGraphics.blendMode = 1;
 	self.dx = 0;
@@ -226,8 +225,25 @@
 		}
 		return false;
 	};
 });
+var EnemyBullet = Container.expand(function () {
+	var self = Container.call(this);
+	var bulletGraphics = self.addChild(XS.getAsset('bullet', 'Bullet', .5, .5));
+	bulletGraphics.y -= 150;
+	bulletGraphics.blendMode = 1;
+	self.dx = 0;
+	self.dy = 0;
+	self.move = function () {
+		self.dx *= 1.02;
+		self.dy *= 1.02;
+		self.setPosition(self.x + self.dx * 4, self.y + self.dy * 4);
+		if (self.x < 150 || self.x > 2048 - 150 || self.y < 700 || self.y > 2732 - 150) {
+			return true;
+		}
+		return false;
+	};
+});
 var Background = Container.expand(function () {
 	var self = Container.call(this);
 	var backgroundGraphics = XS.getAsset('background', 'Background', .5, .5);
 	backgroundGraphics.x = 2048 / 2;