/**** 
* Classes
****/
// No assets are defined as this is a blank game
var Hero = Container.expand(function () {
	var self = Container.call(this);
	self.attachAsset('hero', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 5;
	self.direction = {
		x: 0,
		y: 0
	};
	self.checkCollision = function (trees) {
		for (var i = 0; i < trees.length; i++) {
			if (self.intersects(trees[i])) {
				return true;
			}
		}
		return false;
	};
});
var Tree = Container.expand(function () {
	var self = Container.call(this);
	self.attachAsset('tree', {
		anchorX: 0.5,
		anchorY: 0.5
	});
});
var Bullet = Container.expand(function () {
	var self = Container.call(this);
	self.attachAsset('bullet', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 10;
	self.direction = {
		x: 1,
		y: 0
	};
	self.move = function () {
		self.x += self.direction.x * self.speed;
		self.y += self.direction.y * self.speed;
		if (self.x < 0 || self.x > 2048 || self.y < 0 || self.y > 2732) {
			self.destroy();
		}
	};
});

/**** 
* Initialize Game
****/
var game = new LK.Game({
	backgroundColor: 0x000000 // Initialize game with black background
});

/**** 
* Game Code
****/
var hero = game.addChild(new Hero());
hero.x = 2048 / 2;
hero.y = 2732 / 2;
var dragNode = null;
function handleMove(obj) {
	var event = obj.event;
	var pos = event.getLocalPosition(game);
	if (dragNode) {
		var oldX = dragNode.x;
		var oldY = dragNode.y;
		dragNode.x += (pos.x - dragNode.x) * 0.05;
		dragNode.y += (pos.y - dragNode.y) * 0.05;
		if (dragNode === hero) {
			if (hero.checkCollision(trees)) {
				dragNode.x = oldX;
				dragNode.y = oldY;
			} else {
				hero.direction.x = (pos.x - hero.x) / Math.sqrt(Math.pow(pos.x - hero.x, 2) + Math.pow(pos.y - hero.y, 2));
				hero.direction.y = (pos.y - hero.y) / Math.sqrt(Math.pow(pos.x - hero.x, 2) + Math.pow(pos.y - hero.y, 2));
			}
		}
	}
}
game.on('move', handleMove);
game.on('down', function (obj) {
	dragNode = hero;
	handleMove(obj);
});
game.on('up', function (obj) {
	dragNode = null;
});
game.on('rightdown', function (obj) {
	var bullet = game.addChild(new Bullet());
	bullet.x = hero.x;
	bullet.y = hero.y;
	bullet.direction = {
		x: hero.direction.x,
		y: hero.direction.y
	};
});
// Add trees
for (var i = 0; i < 10; i++) {
	var tree = game.addChild(new Tree());
	tree.x = Math.random() * 2048;
	tree.y = Math.random() * 2732;
}

===================================================================
--- original.js
+++ change.js
@@ -12,8 +12,16 @@
 	self.direction = {
 		x: 0,
 		y: 0
 	};
+	self.checkCollision = function (trees) {
+		for (var i = 0; i < trees.length; i++) {
+			if (self.intersects(trees[i])) {
+				return true;
+			}
+		}
+		return false;
+	};
 });
 var Tree = Container.expand(function () {
 	var self = Container.call(this);
 	self.attachAsset('tree', {
@@ -58,13 +66,20 @@
 function handleMove(obj) {
 	var event = obj.event;
 	var pos = event.getLocalPosition(game);
 	if (dragNode) {
+		var oldX = dragNode.x;
+		var oldY = dragNode.y;
 		dragNode.x += (pos.x - dragNode.x) * 0.05;
 		dragNode.y += (pos.y - dragNode.y) * 0.05;
 		if (dragNode === hero) {
-			hero.direction.x = (pos.x - hero.x) / Math.sqrt(Math.pow(pos.x - hero.x, 2) + Math.pow(pos.y - hero.y, 2));
-			hero.direction.y = (pos.y - hero.y) / Math.sqrt(Math.pow(pos.x - hero.x, 2) + Math.pow(pos.y - hero.y, 2));
+			if (hero.checkCollision(trees)) {
+				dragNode.x = oldX;
+				dragNode.y = oldY;
+			} else {
+				hero.direction.x = (pos.x - hero.x) / Math.sqrt(Math.pow(pos.x - hero.x, 2) + Math.pow(pos.y - hero.y, 2));
+				hero.direction.y = (pos.y - hero.y) / Math.sqrt(Math.pow(pos.x - hero.x, 2) + Math.pow(pos.y - hero.y, 2));
+			}
 		}
 	}
 }
 game.on('move', handleMove);