title: Sprite Kit iOS 7 - how to add a shadow to a SKSpriteNode?
body: <p>I have a <code>SKSpriteNode</code> containing other <code>SKSpriteNodes</code>. How can I create a copy of this <code>SKSpriteNode</code> where all the pixels are black?</p>
  
  <p>Once I have this shadow <code>SKSpriteNode</code> I will then flip it upside down and use it as a shadow.</p>
  
  <p>Thanks</p>