var FrameRateCounter = Container.expand(function () {
	var self = Container.call(this);
	self.lastTime = Date.now();
	self.frameCount = 0;
	self.framerate = 0;
	self.display = new Text2('FPS: 0', {
		size: 150,
		fill: '#ffffff'
	});
	self.display.anchor.set(1, 0);
	self.updateDisplay = function () {
		self.display.setText('FPS: ' + Math.round(self.framerate).toString());
	};
	self.update = function () {
		var currentTime = Date.now();
		var deltaTime = (currentTime - self.lastTime) / 1000;
		self.frameCount++;
		if (deltaTime >= 1) {
			self.framerate = self.frameCount / deltaTime;
			self.updateDisplay();
			self.frameCount = 0;
			self.lastTime = currentTime;
		}
	};
});
var Plain = Container.expand(function () {
	var self = Container.call(this);
	var plainGraphics = self.createAsset('correct_plain_asset_id', 'Correct Plain Graphics Description', .5, .5);
	plainGraphics.scale.x = 2;
	plainGraphics.scale.y = 2;
	plainGraphics.alpha = 1;
	self.shoot = function (enemies, bulletsContainer) {
		if (self.cooldownTimer <= 0 && enemies.length > 0) {
			var bullet = new Bullet(self, game);
			bullet.x = self.x;
			bullet.y = self.y;
			bulletsContainer.addChild(bullet);
			self.cooldownTimer = self.cooldown;
		}
		self.cooldownTimer--;
	};
});
var Tower = Container.expand(function () {
	var self = Container.call(this);
	self.game = game;
	var towerGraphics = self.createAsset('tower', 'Tower Graphics', .5, .5);
	self.cooldown = 30;
	self.cooldownTimer = 0;
	self.shoot = function (enemies, bulletsContainer) {
		if (self.cooldownTimer <= 0 && enemies.length > 0) {
			var bullet = new Bullet(self, self.game);
			bullet.x = self.x;
			bullet.y = self.y;
			bulletsContainer.addChild(bullet);
			bulletsContainer.bullets.push(bullet);
			self.cooldownTimer = self.cooldown;
		}
		self.cooldownTimer--;
	};
});
var Enemy = Container.expand(function () {
	var self = Container.call(this);
	self.game = game;
	var enemyGraphics = self.createAsset('enemy', 'Enemy Graphics', .5, .5);
	self.move = function () {
		self.y += 2;
		if (self.y > 2732) {
			self.destroy();
		}
	};
});
var Bullet = Container.expand(function () {
	var self = Container.call(this);
	self.game = self.parent;
	self.update = function (enemies, scoreTxt) {
		self.move();
		for (var j = enemies.length - 1; j >= 0; j--) {
			if (self.intersects(enemies[j])) {
				enemies[j].destroy();
				enemies.splice(j, 1);
				self.parent.incrementScore();
				self.parent.game.gold += 50;
				self.destroy();
				break;
			}
		}
		if (self.isDestroyed) {
			var index = self.parent.bullets.indexOf(self);
			if (index > -1) {
				self.parent.bullets.splice(index, 1);
			}
		}
	};
	var bulletGraphics = self.createAsset('bullet', 'Bullet Graphics', .5, .5);
	self.move = function () {
		self.x += 10;
		if (self.x > 2048) {
			self.destroy();
		}
	};
});
var Game = Container.expand(function () {
	var self = Container.call(this);
	this.moveEnemies = function () {
		if (this.enemies) {
			this.enemies.forEach(function (enemy) {
				enemy.move();
			});
		}
	};
	self.score = 0;
	self.gold = 100;
	self.incrementScore = function () {
		this.score++;
	};
	self.frameRateCounter = new FrameRateCounter();
	LK.gui.topRight.addChild(self.frameRateCounter.display);
	var enemiesSpawnedLastRound = 1;
	self.scoreTxt = new Text2(self.score.toString(), {
		size: 150,
		fill: "#ffffff"
	});
	self.scoreTxt.anchor.set(0.5, 0);
	LK.gui.topCenter.addChild(self.scoreTxt);
	self.goldTxt = new Text2(self.gold.toString(), {
		size: 150,
		fill: "#ffff00"
	});
	self.goldTxt.anchor.set(0, 0);
	LK.gui.topLeft.addChild(self.goldTxt);
	LK.stageContainer.setBackgroundColor(0xFFFFFF);
	var towers = [];
	self.enemies = [];
	self.bullets = [];
	var initialTower = new Tower();
	initialTower.x = 0 + initialTower.width / 2;
	initialTower.y = 500 + initialTower.height / 2;
	towers.push(initialTower);
	self.addChild(initialTower);
	var plain = self.addChild(new Plain());
	plain.x = 2048 / 2;
	plain.y = 2732 / 2;
	self.addChild(plain);
	var enemy = new Enemy();
	enemy.x = 2048 / 2;
	enemy.y = -enemy.height / 2;
	self.enemies.push(enemy);
	self.addChild(enemy);
	stage.on('down', function (obj) {
		var event = obj.event;
		var pos = event.getLocalPosition(self);
		if (self.gold >= 50) {
			var newTower = new Tower(this);
			newTower.x = pos.x;
			newTower.y = pos.y;
			self.addChild(newTower);
			towers.push(newTower);
			self.gold -= 50;
			self.goldTxt.setText(self.gold.toString());
		}
	});
	LK.on('tick', function () {
		self.frameRateCounter.update();
		if (self.enemies.length === 0) {
			var enemyCount = Math.max(2, enemiesSpawnedLastRound * 2);
			for (var i = 0; i < enemyCount; i++) {
				var newEnemy = new Enemy();
				newEnemy.x = Math.random() * 2048;
				newEnemy.y = -50 * (i + 1);
				self.enemies.push(newEnemy);
				self.addChild(newEnemy);
			}
			enemiesSpawnedLastRound = enemyCount;
		} else {
			towers.forEach(function (tower) {
				tower.shoot(self.enemies, self);
			});
		}
		self.moveEnemies();
		self.bullets.forEach(function (bullet, index) {
			bullet.update(self.enemies);
			if (bullet.isDestroyed) {
				self.score++;
				self.gold += 50;
				self.scoreTxt.setText(self.score.toString());
				self.goldTxt.setText(self.gold.toString());
				self.bullets.splice(index, 1);
			}
		});
	});
});

===================================================================
--- original.js
+++ change.js
@@ -78,9 +78,9 @@
 			if (self.intersects(enemies[j])) {
 				enemies[j].destroy();
 				enemies.splice(j, 1);
 				self.parent.incrementScore();
-				self.game.gold += 50;
+				self.parent.game.gold += 50;
 				self.destroy();
 				break;
 			}
 		}