var Player = Container.expand(function () {
	var self = Container.call(this);
	var playerGraphics = self.createAsset('player', 'Player character', .5, .5);
	self.gravity = 1;
	self.jumpForce = 20;
	self.velocityX = 0;
	self.velocityY = 0;
	self.setJumpForce = function (x, y) {
		var dx = this.x - x;
		var dy = this.y - y;
		this.jumpForceX = dx / 10;
		this.jumpForceY = dy / 10;
	};
	self.update = function () {
		this.x += this.velocityX;
		this.y += this.velocityY;
		this.velocityY += this.gravity;
		if (this.y > 2732) {
			this.y = 2732;
			this.velocity = 0;
		}
	};
});
var Platform = Container.expand(function () {
	var self = Container.call(this);
	var platformGraphics = self.createAsset('platform', 'Platform', .5, .5);
	self.speed = 5;
	self.move = function () {
		this.y += this.speed;
	};
});
var Game = Container.expand(function () {
	var self = Container.call(this);
	stage.on('up', function (obj) {
		if (dragStart) {
			player.velocityX = -player.jumpForceX;
			player.velocityY = -player.jumpForceY;
			dragStart = null;
		}
	});
	stage.on('move', function (obj) {
		if (dragStart) {
			var pos = obj.event.getLocalPosition(self);
			player.setJumpForce(dragStart.x, dragStart.y);
		}
	});
	var platforms = [];
	var ground = self.createAsset('ground', 'Ground', 0, 1);
	ground.y = 2732;
	ground.speed = 5;
	ground.move = function () {
		this.y += this.speed;
		if (this.y > 2732) {
			this.y = 0;
		}
	};
	var player = self.addChild(new Player());
	player.x = 2048 / 2;
	player.y = ground.y - player.height;
	var firstJump = false;
	for (var i = 0; i < 5; i++) {
		var platform = new Platform();
		platform.x = Math.random() * 2048;
		platform.y = i * (2732 / 5);
		platforms.push(platform);
		self.addChild(platform);
	}
	LK.on('tick', function () {
		player.update();
		if (firstJump) {
			ground.move();
			for (var i = 0; i < platforms.length; i++) {
				platforms[i].move();
				if (platforms[i].y > 2732) {
					platforms[i].y = 0;
					platforms[i].x = Math.random() * 2048;
				}
				if (player.intersects(platforms[i]) && player.velocity > 0) {
					player.jump();
				}
			}
		}
	});
	var dragStart = null;
	stage.on('down', function (obj) {
		dragStart = obj.event.getLocalPosition(self);
	});
});

===================================================================
--- original.js
+++ change.js
@@ -2,17 +2,20 @@
 	var self = Container.call(this);
 	var playerGraphics = self.createAsset('player', 'Player character', .5, .5);
 	self.gravity = 1;
 	self.jumpForce = 20;
-	self.velocity = 0;
+	self.velocityX = 0;
+	self.velocityY = 0;
 	self.setJumpForce = function (x, y) {
 		var dx = this.x - x;
 		var dy = this.y - y;
-		this.jumpForce = Math.sqrt(dx * dx + dy * dy) / 10;
+		this.jumpForceX = dx / 10;
+		this.jumpForceY = dy / 10;
 	};
 	self.update = function () {
-		this.y += this.velocity;
-		this.velocity += this.gravity;
+		this.x += this.velocityX;
+		this.y += this.velocityY;
+		this.velocityY += this.gravity;
 		if (this.y > 2732) {
 			this.y = 2732;
 			this.velocity = 0;
 		}
@@ -29,9 +32,10 @@
 var Game = Container.expand(function () {
 	var self = Container.call(this);
 	stage.on('up', function (obj) {
 		if (dragStart) {
-			player.velocity = -player.jumpForce;
+			player.velocityX = -player.jumpForceX;
+			player.velocityY = -player.jumpForceY;
 			dragStart = null;
 		}
 	});
 	stage.on('move', function (obj) {