         layoutItemViews()
     }
     
-    private func viewDidPanHorizontally(view: UIView, byOffset offset: CGFloat) {
+    // TODO: change name now that view can be nil
+    private func viewDidPanHorizontally(view: UIView?, byOffset offset: CGFloat) {
         // TODO: clean this up
         
         // Calculate the new x origin point for the view that was panned.

    private var itemViews: [UIView] = []
    // TODO: clean up property names here
    private var transformView = TransformView()
    private var rootOffset = CGFloat(0)
    private var viewPositions: [UIView: Point3D] = [:]
    
    var decelerateDisplayLinkProgressor: DisplayLinkProgressor?

                velocityX += force * timeDelta
                let offset = velocityX * timeDelta
                
                self.viewDidPanHorizontally(nil, byOffset: CGFloat(offset))
                
                print("force: \(force), time: \(timeDelta), offset: \(offset), speed: \(velocityX)")

