     // Add gravity to the animator
     self.animator!.addBehavior(self.gravity)
     self.animator!.addBehavior(self.collision)
+    
+    // add pan getsture recognizer
+    self.panGesture = UIPanGestureRecognizer(target: self, action: "panning:")
+    self.greenBox!.addGestureRecognizer(panGesture!)
   }
   
   override func didReceiveMemoryWarning() {

    // Dispose of any resources that can be recreated.
  }
  
}

  var animator: UIDynamicAnimator?
  var gravity: UIGravityBehavior?
  var collision: UICollisionBehavior?
  
  var panGesture: UIPanGestureRecognizer?
  
  override func viewDidLoad() {
    super.viewDidLoad()
