let image = self.overlayImageView[cell1]

    image.clipsToBounds = true

    image.center.x -= image.bounds.width

    UIView.animateWithDuration(0.75, animations: { () -> Void in

        image.center.x += image.bounds.width

    }) { (Bool) -> Void in

        //completion handler

    }

cell.clipsToBounds = true

    button.clipsToBounds = true

    let image = UIImage(named: answeredCorrectlyImage)

    button.addSubview(cell) //this was all that was missing

    cell.center.x -= cell.bounds.width

    if users == 1...5 && cell.hidden == true {

        button.enabled = false

        cell.hidden = false

        cell.image = image

        UIView.animateWithDuration(2.0, animations: { () -> Void in

            cell.center.x += cell.bounds.width

        })