class FirstCustomSegue: UIStoryboardSegue {

override func perform() {
    // Value of type 'FirstCustomSegue' has no member 'sourceGameViewController'
    var firstVCView = self.sourceGameViewController.view as UIView!
    var secondVCView = self.destinationGameViewController.view as UIView!

    // Cannot call value of non-function type 'UIScreen'
    let screenWidth = UIScreen.mainScreen().bounds.size.width
    let screenHeight = UIScreen.mainScreen().bounds.size.height

    secondVCView.frame = CGRectMake(0.0, screenHeight, screenWidth, screenHeight)

    // Cannot call value of non-function type 'UIApplication'
    let window = UIApplication.sharedApplication().keyWindow
    window?.insertSubview(secondVCView, aboveSubview: firstVCView)

    // Value of type 'FirstCustomSegue' has no member 'sourceGameViewController' (This is in the (Finished) line, of course)

    UIView.animateWithDuration(0.4, animations: { () -> Void in
        firstVCView.frame = CGRectOffset(firstVCView.frame, 0.0, -screenHeight)
        secondVCView.frame = CGRectOffset(secondVCView.frame, 0.0, -screenHeight)

    }) { (Finished) -> Void inself.sourceGameViewController.presentGameViewController(self.destinationGameViewController as UIViewController,
                animated: false,
                completion: nil)
    }
}

}