var Tower = Container.expand(function () {
	var self = Container.call(this);
	self.scheduleNextSnowball = function () {};
	self.isActive = false;
	self.upgradeCost = 5;
	self.snowballSpeed = 5;
	self.activationCost = 5;
	self.activateTower = function () {
		if (self.gameInstance.coins >= self.activationCost) {
			self.gameInstance.coins -= self.activationCost;
			self.isActive = true;
			self.activationCost *= 2;
			self.gameInstance.coinDisplay.setText('Coins: ' + self.gameInstance.coins);
			self.gameInstance.towerCostText.setText(self.activationCost.toString());
			self.shootSnowball();
		} else {
			console.log('Not enough coins to activate the tower');
		}
	};
	self.upgradeTower = function () {
		if (self.gameInstance.coins >= self.upgradeCost) {
			self.snowballSpeed += 2;
			self.gameInstance.coins -= self.upgradeCost;
			self.upgradeCost += 5;
			self.gameInstance.coinDisplay.setText('Coins: ' + self.gameInstance.coins);
			self.gameInstance.towerCostText.setText(self.upgradeCost.toString());
		} else {
			console.log('Not enough coins to upgrade the tower');
		}
	};
	self.shootSnowball = function () {
		if (self.isActive && self.gameInstance.bullets.length === 0) {
			var snowball = new Snowball(self.snowballSpeed);
			snowball.x = self.x;
			snowball.y = self.y + 130;
			self.gameInstance.bullets.push(snowball);
			self.parent.addChild(snowball);
		}
	};
});
var Snowball = Container.expand(function (speed) {
	var self = Container.call(this);
	self.speed = speed;
	var snowballGraphics = self.createAsset('snowball', 'Snowball Graphics', .5, .5);
	self.speed = speed;
});
var Base = Container.expand(function () {
	var self = Container.call(this);
	self.health = 100;
	self.updateHealth = function () {};
});
var Enemy = Container.expand(function (spawnerInstance, gameInstance) {
	var self = Container.call(this);
	self.gameInstance = gameInstance;
	var enemyGraphics = self.createAsset('enemy', 'Enemy Graphics', .5, .5);
	self.speed = 4;
	self.move = function () {
		self.y += self.speed;
	};
	self.on('down', function () {
		self.destroyEnemy();
	});
	self.destroyEnemy = function () {
		self.destroy();
		self.gameInstance.updateCoins(1);
		self.gameInstance.enemies = self.gameInstance.enemies.filter(function (e) {
			return e !== self;
		});
	};
});
var Spawner = Container.expand(function (x, y) {
	var self = Container.call(this);
	var spawnerGraphics = self.createAsset('spawner', 'Spawner Graphics', .5, .5);
	self.x = x;
	self.y = y;
	self.spawnEnemy = function () {
		var enemy = new Enemy(self, self.parent);
		enemy.x = self.x;
		enemy.y = self.y;
		self.parent.enemies.push(enemy);
		self.parent.addChild(enemy);
	};
});
var Game = Container.expand(function () {
	var self = Container.call(this);
	self.shootSnowball = function () {
		if (self.tower) {
			self.tower.shootSnowball();
		}
	};
	self.towerButton = self.createAsset('towerButton', 'Tower Button', .5, .5);
	self.towerButton.x = 2048 / 2 - 900;
	self.towerButton.y = 1800 - 1300;
	var towerCenterX = self.towerButton.x + self.towerButton.width * 0.5;
	var towerCenterY = self.towerButton.y + self.towerButton.height * 0.5;
	self.towerButton.on('down', function () {
		if (self.tower) {
			if (!self.tower.isActive) {
				self.tower.activateTower();
			} else {
				self.tower.upgradeTower();
			}
		}
	});
	LK.gui.addChild(self.towerButton);
	var background = self.createAsset('background', 'Game Background', 0, 0);
	background.width = LK.stage.width;
	background.height = LK.stage.height;
	self.coins = 0;
	self.coinDisplay = new Text2('Coins: 0', {
		size: 100,
		fill: "#ffffff",
		align: 'center',
		stroke: '#000000',
		strokeThickness: 6
	});
	self.coinDisplay.anchor.set(0.5, 0.5);
	self.coinDisplay.x = 2048 / 2;
	self.coinDisplay.y = 1600;
	LK.gui.addChild(self.coinDisplay);
	self.removeCoinDisplay = function () {
		LK.gui.removeChild(self.coinDisplay);
	};
	self.towerButton = self.createAsset('towerButton', 'Tower Button', .5, .5);
	self.towerButton.x = 2048 / 2 - 900;
	self.towerButton.y = 1800 - 1300;
	self.towerButton.interactive = true;
	LK.gui.addChild(self.towerButton);
	var towerCost = 5;
	self.towerCostText = new Text2(towerCost.toString(), {
		size: 50,
		fill: "#ffffff",
		align: 'center'
	});
	self.towerCostText.anchor.set(0.5, 0.5);
	self.towerCostText.x = self.towerButton.x;
	self.towerCostText.y = self.towerButton.y;
	LK.gui.addChild(self.towerCostText);
	self.updateCoins = function (coinIncrement) {
		self.coins += coinIncrement;
		self.coinDisplay.setText('Coins: ' + self.coins);
		if (self.coins >= 5) {
			self.towerButton.interactive = true;
		}
	};
	self.enemies = [];
	var base = self.addChild(new Base());
	self.bullets = [];
	self.snowballSpeed = 7;
	self.tower = self.addChild(new Tower());
	self.tower.x = towerCenterX;
	self.tower.y = towerCenterY;
	self.tower.gameInstance = self;
	base.x = 2048 / 2;
	base.y = 2732 - base.height / 2;
	var spawner1 = self.addChild(new Spawner(2048 / 6 + 200, 200));
	var spawner2 = self.addChild(new Spawner(2048 / 2 + 100, 200));
	var spawner3 = self.addChild(new Spawner(2048 / 6 * 5, 200));
	var spawner1Timer = LK.setInterval(function () {
		spawner1.spawnEnemy();
	}, 2000);
	spawner1.spawnEnemy();
	var spawner2Timer = LK.setInterval(function () {
		spawner2.spawnEnemy();
	}, 2500);
	spawner2.spawnEnemy();
	var spawner3Timer = LK.setInterval(function () {
		spawner3.spawnEnemy();
	}, 3000);
	spawner3.spawnEnemy();
	LK.on('tick', function () {
		self.enemies.forEach(function (enemy) {
			enemy.move();
			if (enemy.y + enemy.height / 2 >= LK.stage.height) {
				self.removeCoinDisplay();
				LK.showGameOver();
			}
		});
		self.bullets.forEach(function (snowball) {
			snowball.x += snowball.speed;
			self.enemies.forEach(function (enemy) {
				if (snowball.intersects(enemy)) {
					enemy.destroyEnemy();
				}
			});
			if (snowball.x > LK.stage.width) {
				self.bullets = self.bullets.filter(function (b) {
					return b !== snowball;
				});
				snowball.destroy();
				if (self.tower.isActive) {
					self.tower.shootSnowball();
				}
			}
		});
	});
});

===================================================================
--- original.js
+++ change.js
@@ -8,9 +8,9 @@
 	self.activateTower = function () {
 		if (self.gameInstance.coins >= self.activationCost) {
 			self.gameInstance.coins -= self.activationCost;
 			self.isActive = true;
-			self.activationCost += 5;
+			self.activationCost *= 2;
 			self.gameInstance.coinDisplay.setText('Coins: ' + self.gameInstance.coins);
 			self.gameInstance.towerCostText.setText(self.activationCost.toString());
 			self.shootSnowball();
 		} else {