var Hero = Container.expand(function () {
	var self = Container.call(this);
	var heroGraphics = self.createAsset('hero', 'Hero character', .5, .5);
	self.move = function () {};
	self.shoot = function () {};
});
var EnemyWave1 = Container.expand(function () {
	var self = Container.call(this);
	var enemyGraphics = self.createAsset('enemyWave1', 'Enemy Wave 1 character', .5, .5);
	self.move = function () {};
});
var EnemyWave2 = Container.expand(function () {
	var self = Container.call(this);
	var enemyGraphics = self.createAsset('enemyWave2', 'Enemy Wave 2 character', .5, .5);
	self.move = function () {};
});
var EnemyWave3 = Container.expand(function () {
	var self = Container.call(this);
	var enemyGraphics = self.createAsset('enemyWave3', 'Enemy Wave 3 character', .5, .5);
	self.move = function () {};
});
var HeroBullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.createAsset('heroBullet', 'Hero Bullet', .5, .5);
	self.move = function () {};
});
var EnemyBullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.createAsset('enemyBullet', 'Enemy Bullet', .5, .5);
	self.move = function () {};
});
var Game = Container.expand(function () {
	var self = Container.call(this);
	var hero = self.addChild(new Hero());
	var enemies = [];
	var waveIndex = 0;
	var waveTimer = 0;
	var waveInterval = 300;
	var enemiesPerWave = 5;
	var heroBullets = [];
	var enemyBullets = [];
	hero.x = 2048 / 2;
	hero.y = 2732 / 2;
	LK.on('tick', function () {
		hero.move();
		waveTimer++;
		if (waveTimer >= waveInterval) {
			for (var i = 0; i < enemiesPerWave; i++) {
				var newEnemy;
				switch (waveIndex % 3) {
					case 0:
						newEnemy = new EnemyWave1();
						break;
					case 1:
						newEnemy = new EnemyWave2();
						break;
					case 2:
						newEnemy = new EnemyWave3();
						break;
				}
				newEnemy.x = Math.random() * 2048;
				newEnemy.y = -100;
				enemies.push(newEnemy);
				self.addChild(newEnemy);
			}
			waveIndex++;
			waveTimer = 0;
		}
		for (var i = 0; i < enemies.length; i++) {
			enemies[i].move();
		}
		for (var i = 0; i < heroBullets.length; i++) {
			heroBullets[i].move();
		}
		for (var i = 0; i < enemyBullets.length; i++) {
			enemyBullets[i].move();
		}
	});
	stage.on('down', function (obj) {
		var pos = obj.event.getLocalPosition(self);
		hero.x = pos.x;
		hero.y = pos.y;
		hero.shoot();
	});
});

===================================================================
--- original.js
+++ change.js
@@ -3,13 +3,23 @@
 	var heroGraphics = self.createAsset('hero', 'Hero character', .5, .5);
 	self.move = function () {};
 	self.shoot = function () {};
 });
-var Enemy = Container.expand(function () {
+var EnemyWave1 = Container.expand(function () {
 	var self = Container.call(this);
-	var enemyGraphics = self.createAsset('enemy', 'Enemy character', .5, .5);
+	var enemyGraphics = self.createAsset('enemyWave1', 'Enemy Wave 1 character', .5, .5);
 	self.move = function () {};
 });
+var EnemyWave2 = Container.expand(function () {
+	var self = Container.call(this);
+	var enemyGraphics = self.createAsset('enemyWave2', 'Enemy Wave 2 character', .5, .5);
+	self.move = function () {};
+});
+var EnemyWave3 = Container.expand(function () {
+	var self = Container.call(this);
+	var enemyGraphics = self.createAsset('enemyWave3', 'Enemy Wave 3 character', .5, .5);
+	self.move = function () {};
+});
 var HeroBullet = Container.expand(function () {
 	var self = Container.call(this);
 	var bulletGraphics = self.createAsset('heroBullet', 'Hero Bullet', .5, .5);
 	self.move = function () {};
@@ -35,9 +45,20 @@
 		hero.move();
 		waveTimer++;
 		if (waveTimer >= waveInterval) {
 			for (var i = 0; i < enemiesPerWave; i++) {
-				var newEnemy = new Enemy();
+				var newEnemy;
+				switch (waveIndex % 3) {
+					case 0:
+						newEnemy = new EnemyWave1();
+						break;
+					case 1:
+						newEnemy = new EnemyWave2();
+						break;
+					case 2:
+						newEnemy = new EnemyWave3();
+						break;
+				}
 				newEnemy.x = Math.random() * 2048;
 				newEnemy.y = -100;
 				enemies.push(newEnemy);
 				self.addChild(newEnemy);