title: SkSpriteNode position in universal game
body: <p>I'm creating universal game for all iOS devices in portrait mode using Swift. In GameViewController I'm creating scene like this:</p>
  
  <pre><code>let scene = GameScene(size:CGSize(width: 1536, height: 2048))
  scene.scaleMode = .AspectFill
  </code></pre>
  
  <p>Background image has resolution 1536x2048, and so with above scaleMode on iPad it's displayed in its full size, on iPhone 6 1152x2048 is displayed with sides trimmed. Works perfectly fine on all devices, and only one background image is needed. Problem is that if I call for size.width or self.frame.size.width it always returns 1536, even if the actual visible area is e.g. 1152.</p>
  
  <p>How can I set SkSpriteNode's position relative to visible area, so that it'll be for example 50x50 from the corner on every device?</p>