 
 // MARK: Transition delegate
 
-extension LightboxTransition : UIViewControllerTransitioningDelegate {
+private extension LightboxTransition : UIViewControllerTransitioningDelegate {
 
   func animationControllerForPresentedController(presented: UIViewController,
     presentingController presenting: UIViewController,


// MARK: Transitioning delegate

extension LightboxTransition : UIViewControllerAnimatedTransitioning {

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

import UIKit

private class LightboxTransition: NSObject {

  struct Timing {
    static let Transition: NSTimeInterval = 0.4
