 import UIKit
 
-class LightboxTransition: NSObject {
+private class LightboxTransition: NSObject {
 
   struct Timing {
     static let Transition: NSTimeInterval = 0.4


// MARK: Transitioning delegate

extension LightboxTransition : UIViewControllerAnimatedTransitioning {

  func transitionDuration(transitionContext: UIViewControllerContextTransitioning) -> NSTimeInterval {
    return Timing.Transition


// MARK: Transition delegate

private extension LightboxTransition : UIViewControllerTransitioningDelegate {

  func animationControllerForPresentedController(presented: UIViewController,
    presentingController presenting: UIViewController,
