 private class DraggingProxy: UIImageView {
     var fromIndexPath: NSIndexPath?
     var fromCenter = CGPoint.zeroPoint
+    var initialCenter = CGPoint.zeroPoint
 
     init(cell: UICollectionViewCell) {
         super.init(frame: CGRect.zeroRect)

        switch recognizer.state {
        case .Changed:
            if let proxy = dragProxy {
                proxy.center.x = proxy.fromCenter.x + translation.x
                //TODO: Constrain to be within collectionView.frame:
                // proxy.center.y = proxy.fromCenter.y + translation.y
            }
        default:
            break

                let proxy = DraggingProxy(cell: cell)
                proxy.fromIndexPath = indexPath
                proxy.frame = cell.bounds
                proxy.initialCenter = cell.center
                proxy.fromCenter = cell.center
                proxy.center = proxy.fromCenter

