var Hero = Container.expand(function () {
	var self = Container.call(this);
	var heroGraphics = self.createAsset('hero', 'Hero character', .5, .5);
	self.speed = 5;
	self.move = function () {};
	self.jump = function () {};
	self.shoot = function () {};
	self.update = function () {};
});
var Enemy = Container.expand(function () {
	var self = Container.call(this);
	var enemyGraphics = self.createAsset('enemy', 'Enemy character', .5, .5);
	self.speed = 3;
	self.move = function () {};
	self.attack = function () {};
});
var HeroBullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.createAsset('heroBullet', 'Hero Bullet', .5, .5);
	self.speed = 10;
	self.move = function () {};
});
var EnemyBullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.createAsset('enemyBullet', 'Enemy Bullet', .5, .5);
	self.speed = 7;
	self.move = function () {};
});
var Game = Container.expand(function () {
	var self = Container.call(this);
	var hero = self.addChild(new Hero());
	var enemies = [];
	var heroBullets = [];
	var enemyBullets = [];
	hero.x = 1024;
	hero.y = 1366;
	LK.on('tick', function () {
		hero.update();
		for (var i = 0; i < enemies.length; i++) {
			enemies[i].update();
		}
		for (var i = 0; i < heroBullets.length; i++) {
			heroBullets[i].update();
		}
		for (var i = 0; i < enemyBullets.length; i++) {
			enemyBullets[i].update();
		}
	});
	self.on('down', function (obj) {
		var event = obj.event;
		var pos = event.getLocalPosition(self);
		if (pos.x > hero.x) {
			hero.move();
		} else {
			hero.shoot();
		}
	});
});

===================================================================
--- original.js
+++ change.js
@@ -4,8 +4,9 @@
 	self.speed = 5;
 	self.move = function () {};
 	self.jump = function () {};
 	self.shoot = function () {};
+	self.update = function () {};
 });
 var Enemy = Container.expand(function () {
 	var self = Container.call(this);
 	var enemyGraphics = self.createAsset('enemy', 'Enemy character', .5, .5);