title: add another background image to change background during playing game
body: <pre><code>func createBackgrounds() {
      for i in 0...2 {
         let bg = SKSpriteNode(imageNamed: "BG Day")
         bg.name = "BG"
         bg.zPosition = 0;
         bg.anchorPoint = CGPoint(x: 0.5, y: 0.5)
         bg.position = CGPoint(x: CGFloat(i) * bg.size.width, y: 0)
         self.addChild(bg)
      }
  }
  </code></pre>
  
  <p>If I want to add another background image after 2 minutes to <code>BG Night</code>, how can I write coding in swift 2?</p>