     }
     
     /// A reference to the animation elapsed time.
-    open fileprivate(set) var animationElapsedTime: TimeInterval = 0 {
+    open fileprivate(set) var transitionElapsedTime: TimeInterval = 0 {
         didSet {
             guard isTransitioning else {
                 return

            return
        }
        
        guard 0 < animationDuration else {
            return
        }
        
        guard let v = animationStartTime else {
            return
        }
        
        var elapsedTime = CACurrentMediaTime() - v
        
        if elapsedTime > animationDuration {
            animationElapsedTime = isFinished ? 1 : 0
            completeTransition()
            
        } else {
            elapsedTime = elapsedTime / animationDuration
            
            if !isFinished {
                elapsedTime = 1 - elapsedTime
            }
            
            animationElapsedTime = max(0, min(1, elapsedTime))
        }
    }
}

        return nil == displayLink
    }
    
    /// Transition container.
    open fileprivate(set) var transitionContainer: UIView!
    
    /// An Array of from and to view paris to be animated.
    open fileprivate(set) var transitionParis = [(fromViews: [UIView], toViews: [UIView])]()
}

extension MotionController {
