     }
 }
 
+// MARK: - View Controller
+
 class ViewController: UIViewController {
     
+    // MARK: - Constants
+    
     private let popupOffset: CGFloat = 440
+    
+    // MARK: - Views
     
     private lazy var contentImageView: UIImageView = {
         let imageView = UIImageView()

            }
            self.view.layoutIfNeeded()
        })
        transitionAnimator.addCompletion { position in
            switch position {
            case .start:
                self.currentState = state.opposite

            }
        })
        inTitleAnimator.scrubsLinearly = false
        
        // an animator for the title that is transitioning out of view
        let outTitleAnimator = UIViewPropertyAnimator(duration: duration, curve: .easeOut, animations: {
            switch state {
            case .open:
