===================================================================
--- original.js
+++ change.js
@@ -26,8 +26,9 @@
 	var self = Container.call(this);
 	var hero = self.addChild(new Hero());
 	var enemies = [];
 	var isGameOver = false;
+	var lastSpeedIncrease = 0;
 	hero.x = 2048 / 2;
 	hero.y = 2732 / 2;
 	for (var i = 0; i < 5; i++) {
 		var enemy = self.addChild(new Enemy());
@@ -55,8 +56,14 @@
 		touchStart = obj.event.getLocalPosition(self);
 		hero.move(touchStart, touchStart);
 	});
 	LK.on('tick', function () {
+		if (LK.ticks - lastSpeedIncrease >= 300) {
+			for (var i = 0; i < enemies.length; i++) {
+				enemies[i].speed += 1;
+			}
+			lastSpeedIncrease = LK.ticks;
+		}
 		for (var i = 0; i < enemies.length; i++) {
 			enemies[i].chase(hero);
 			if (enemies[i].intersects(hero)) {
 				isGameOver = true;