title: How to make a sprite move up and down forever in swift SpriteKit
body: <p>I am trying to make a sprite move up and down forever, I have tried using an "if statement" which checks if the position is... than it will move up again. But it does not work.
  I would really appreciate some help, thanks!
  Here is the code.</p>
  
  <pre><code>var Ground = SKSpriteNode()
  var Ground2 = SKSpriteNode()
  
  override func didMoveToView(view: SKView) {
      Move()
  }
  
  func Move(){
      let action = SKAction.moveToY(self.frame.height / 2 - 360, duration: 5.0)
      Ground.runAction(SKAction.repeatActionForever(action))
  
      let action2 = SKAction.moveToY(self.frame.height / 2 + 140, duration: 5.0)
      Ground2.runAction(SKAction.repeatActionForever(action2))
  }
  </code></pre>