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 (x, y) {
		self.x += x * self.speed;
		self.y += y * self.speed;
	};
});
var Enemy = Container.expand(function () {
	var self = Container.call(this);
	var enemyGraphics = self.createAsset('enemy', 'Enemy character', .5, .5);
	self.speed = 3;
	self.chase = function (hero) {
		var dx = hero.x - self.x;
		var dy = hero.y - self.y;
		var distance = Math.sqrt(dx * dx + dy * dy);
		self.x += dx / distance * self.speed;
		self.y += dy / distance * self.speed;
	};
});
var Game = Container.expand(function () {
	var self = Container.call(this);
	var hero = self.addChild(new Hero());
	var enemies = [];
	var isGameOver = false;
	hero.x = 2048 / 2;
	hero.y = 2732 / 2;
	for (var i = 0; i < 5; i++) {
		var enemy = self.addChild(new Enemy());
		enemy.x = Math.random() * 2048;
		enemy.y = Math.random() * 2732;
		enemies.push(enemy);
	}
	var touchStart = {
		x: 0,
		y: 0
	};
	var touchEnd = {
		x: 0,
		y: 0
	};
	stage.on('down', function (obj) {
		touchStart = obj.event.getLocalPosition(self);
	});
	stage.on('up', function (obj) {
		touchEnd = obj.event.getLocalPosition(self);
		var dx = touchEnd.x - touchStart.x;
		var dy = touchEnd.y - touchStart.y;
		var distance = Math.sqrt(dx * dx + dy * dy);
		hero.move(dx / distance, dy / distance);
	});
	LK.on('tick', function () {
		for (var i = 0; i < enemies.length; i++) {
			enemies[i].chase(hero);
			if (enemies[i].intersects(hero)) {
				isGameOver = true;
				LK.effects.flashScreen(0xff0000, 1000);
				LK.showGameOver();
			}
		}
	});
});

===================================================================
--- original.js
+++ change.js
@@ -31,12 +31,23 @@
 		enemy.x = Math.random() * 2048;
 		enemy.y = Math.random() * 2732;
 		enemies.push(enemy);
 	}
+	var touchStart = {
+		x: 0,
+		y: 0
+	};
+	var touchEnd = {
+		x: 0,
+		y: 0
+	};
 	stage.on('down', function (obj) {
-		var pos = obj.event.getLocalPosition(self);
-		var dx = pos.x - hero.x;
-		var dy = pos.y - hero.y;
+		touchStart = obj.event.getLocalPosition(self);
+	});
+	stage.on('up', function (obj) {
+		touchEnd = obj.event.getLocalPosition(self);
+		var dx = touchEnd.x - touchStart.x;
+		var dy = touchEnd.y - touchStart.y;
 		var distance = Math.sqrt(dx * dx + dy * dy);
 		hero.move(dx / distance, dy / distance);
 	});
 	LK.on('tick', function () {