Core Motion

 override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)

        let motionManager=AppDelegate.Motion.Manager
        if motionManager.accelerometerAvailable {
            motionManager.startAccelerometerUpdatesToQueue(NSOperationQueue.mainQueue()) { (data, error) -> Void in
                self.bouncer.gravity.gravityDirection=CGVector(dx: data.acceleration.x, dy: -data.acceleration.y)
            }
        }

    }
    override func viewWillDisappear(animated: Bool) {
        super.viewWillDisappear(animated)
        AppDelegate.Motion.Manager.stopAccelerometerUpdates()
    }