title: How to pause and stop SKScene without having performance issues?
body: <p>I am writing a program using Swift3 in Xcode. I am using SpriteKit and SKScene in my program. As you know, there is a predefined update function that always runs (even when the view changed) in gamescene.sks.</p>
  
  <p>I know that "self.scene.view.paused = YES;" does not work for update functions that are always called.</p>
  
  <p>Is there any way to pause and stop SKScene and its update function?</p>