     override var prefersStatusBarHidden: Bool {
         return true
     }
+    
+    // MARK: - Layout
     
     private var bottomConstraint = NSLayoutConstraint()
     

        return recognizer
    }()
    
    private func animateTransitionIfNeeded(to state: State, duration: TimeInterval) {
        guard runningAnimators.isEmpty else { return }
        let transitionAnimator = UIViewPropertyAnimator(duration: duration, dampingRatio: 1, animations: {
            switch state {
            case .open:

            }
            self.view.layoutIfNeeded()
        })
        
        // the transition completion block
        transitionAnimator.addCompletion { position in
            
            // update the state
            switch position {
            case .start:
                self.currentState = state.opposite
