/**** 
* 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 = -10;
	self.update = function () {
		self.y += 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.shoot = function () {
		var bullet = new Bullet();
		bullet.x = self.x;
		bullet.y = self.y - 50;
		bullets.push(bullet);
		game.addChild(bullet);
	};
});
// PowerUp class
var PowerUp = Container.expand(function () {
	var self = Container.call(this);
	var powerUpGraphics = self.attachAsset('powerUp', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.update = function () {
		self.y += 2;
	};
});
//<Assets used in the game will automatically appear here>
//<Write imports for supported plugins here>
// enemy_1 class
var enemy_1 = Container.expand(function () {
	var self = Container.call(this);
	var enemy_1Graphics = self.attachAsset('enemy_a', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 3;
	self.update = function () {
		self.y += self.speed;
	};
});

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

/**** 
* Game Code
****/ 
// Initialize player
var player = game.addChild(new Player());
player.x = 2048 / 2;
player.y = 2500;
// Initialize arrays
var enemy_1s = [];
var bullets = [];
var powerUps = [];
// Initialize enemy_1 group counter
var enemy_1GroupCount = 0;
// Game update function
game.update = function () {
	// Update enemy_1s
	for (var i = enemy_1s.length - 1; i >= 0; i--) {
		var enemy_1 = enemy_1s[i];
		enemy_1.update();
		if (enemy_1.y > 2732) {
			enemy_1.destroy();
			enemy_1s.splice(i, 1);
		}
	}
	// Update bullets
	for (var j = bullets.length - 1; j >= 0; j--) {
		var bullet = bullets[j];
		bullet.update();
		if (bullet.y < 0) {
			bullet.destroy();
			bullets.splice(j, 1);
		}
	}
	// Update power-ups
	for (var k = powerUps.length - 1; k >= 0; k--) {
		var powerUp = powerUps[k];
		powerUp.update();
		if (powerUp.y > 2732) {
			powerUp.destroy();
			powerUps.splice(k, 1);
		}
	}
	// Check for collisions
	checkCollisions();
};
// Function to check for collisions
function checkCollisions() {
	// Check bullet and enemy_1 collisions
	for (var i = bullets.length - 1; i >= 0; i--) {
		var bullet = bullets[i];
		for (var j = enemy_1s.length - 1; j >= 0; j--) {
			var enemy_1 = enemy_1s[j];
			if (bullet.intersects(enemy_1)) {
				bullet.destroy();
				enemy_1.destroy();
				bullets.splice(i, 1);
				enemy_1s.splice(j, 1);
				// Decrement enemy_1 group counter
				enemy_1GroupCount--;
				// Check if a whole group of enemy_1 has been defeated
				if (enemy_1GroupCount % 6 === 0) {
					// Spawn a powerup
					spawnPowerUp();
				}
				break;
			}
		}
	}
	// Check player and power-up collisions
	for (var k = powerUps.length - 1; k >= 0; k--) {
		var powerUp = powerUps[k];
		if (player.intersects(powerUp)) {
			powerUp.destroy();
			powerUps.splice(k, 1);
			// Upgrade player's gun
			player.shoot = function () {
				var bullet1 = new Bullet();
				bullet1.x = self.x - 20;
				bullet1.y = self.y - 50;
				bullets.push(bullet1);
				game.addChild(bullet1);
				var bullet2 = new Bullet();
				bullet2.x = self.x + 20;
				bullet2.y = self.y - 50;
				bullets.push(bullet2);
				game.addChild(bullet2);
			};
		}
	}
}
// Function to spawn enemy_1s
function spawnEnemy_1() {
	var enemy = new enemy_1();
	enemy.x = Math.random() * 2048;
	enemy.y = -50;
	enemy_1s.push(enemy);
	game.addChild(enemy);
	// Increment enemy_1 group counter
	enemy_1GroupCount++;
}
// Function to spawn power-ups
function spawnPowerUp() {
	var powerUp = new PowerUp();
	powerUp.x = Math.random() * 2048;
	powerUp.y = -50;
	powerUps.push(powerUp);
	game.addChild(powerUp);
}
// Set intervals for spawning
LK.setInterval(spawnEnemy_1, 1000);
LK.setInterval(spawnPowerUp, 10000);
// Player controls
game.down = function (x, y, obj) {
	player.x = x;
	player.y = y;
};
game.move = function (x, y, obj) {
	player.x = x;
	player.y = y;
};
game.up = function (x, y, obj) {
	player.shoot();
};

===================================================================
--- original.js
+++ change.js
@@ -71,8 +71,10 @@
 // Initialize arrays
 var enemy_1s = [];
 var bullets = [];
 var powerUps = [];
+// Initialize enemy_1 group counter
+var enemy_1GroupCount = 0;
 // Game update function
 game.update = function () {
 	// Update enemy_1s
 	for (var i = enemy_1s.length - 1; i >= 0; i--) {
@@ -115,8 +117,15 @@
 				bullet.destroy();
 				enemy_1.destroy();
 				bullets.splice(i, 1);
 				enemy_1s.splice(j, 1);
+				// Decrement enemy_1 group counter
+				enemy_1GroupCount--;
+				// Check if a whole group of enemy_1 has been defeated
+				if (enemy_1GroupCount % 6 === 0) {
+					// Spawn a powerup
+					spawnPowerUp();
+				}
 				break;
 			}
 		}
 	}
@@ -148,8 +157,10 @@
 	enemy.x = Math.random() * 2048;
 	enemy.y = -50;
 	enemy_1s.push(enemy);
 	game.addChild(enemy);
+	// Increment enemy_1 group counter
+	enemy_1GroupCount++;
 }
 // Function to spawn power-ups
 function spawnPowerUp() {
 	var powerUp = new PowerUp();