title: Custom SpriteKit "Door open", "Page Turn" transition
body: <p>Is there any documentation or tutorials on creating custom transitions in SpriteKit?
  Is there any way to modify <code>[SKTransition doorwayWithDuration:1];</code> to show only one door, and to open towards the user?</p>
  
  <p>I found this project on github and modified it to use a single door. 
  <a href="https://github.com/mkftr/DoorwayTransition" rel="nofollow">https://github.com/mkftr/DoorwayTransition</a>
  But this only works on Views. Not SKScene. </p>
  
  <p>Is there a way to modify it so that I can get it to work?</p>
  
  <p>I can't find anything out there, documentation or otherwise, explaining any of this. 
  The transitions that come bundled in SpriteKit are too few, and I figured this would be a common problem for many other developers. </p>
  
  <p>Failing all the above, what's the alternative?
  I'm putting together an interactive book, and would really like a decent page turning transition between scenes. </p>
  
  <p>Note though, I'm not looking for "Page Curl", but more of a "Door opening" transition.
  But will settle for "Page Curl" if necessary, and someone can explain how to do it. </p>
  
  <p>The book will only be available on iPad.</p>