title: Best way to convert SKShapeNode to SKSpriteNode
body: <p>I'm creating a simple tetris game in swift to try out sprite kit/swift together. I'm creating tetris as practice using SKShapeNodes to create all the shapes and the game board. Unfortunately this is causing the iPhone's CPU to run at pretty much 100% the entire time the game is playing. In the apple docs it says that the SKShapeNode is not efficient and to use SKSpriteNode instead when possible. My game scales based on the size of the screen so I'd like to create an SKShapeNode then convert that to an SKSpriteNode. I found an example online using textures to accomplish that, but it seems like an ugly solution. Is there a simple/standard way to convert an SKShapeNode to an SKSpriteNode to avoid maxing out the CPU?</p>
  
  <p>Thanks for your help!</p>