     
     public enum Background {
         case opaque(color: UIColor, shadow: Shadow?)
-        case translucent(style: UIBlurEffectStyle)
+        case translucent(style: UIBlurEffectStyle, alpha: CGFloat)
+        case vibrant(style: UIBlurEffectStyle, alpha: CGFloat)
     }
     
     static let speedThreshold: CGFloat = 300.0

            case let .opaque(color, shadow):
                self.sideContainerView.backgroundColor = color
                self.shadow = shadow
            case .translucent:
                self.sideContainerView.backgroundColor = .clear
            }
        }
    }

        self.sideContainerView.hideShadow(animation: 0.0)
        
        switch self.background {
        case let .translucent(style, alpha):
            self.sideContainerView.backgroundColor = UIColor(white: 1.0, alpha: alpha)
            let blurEffect = UIBlurEffect(style: style)
            self.blurView = UIVisualEffectView(effect: blurEffect)
            self.sideContainerView.insertSubview(self.blurView!, at: 0)
            self.pinIntoSideContainer(view: self.blurView!)
            self.addChildViewController(self.sideController)
            self.blurView?.contentView.addSubview(self.sideController.view)
            self.pinIntoSuperView(view: self.sideController.view)
            self.sideController.didMove(toParentViewController: self)
        case let .vibrant(style, alpha):
            self.sideContainerView.backgroundColor = UIColor(white: 1.0, alpha: alpha)
            let blurEffect = UIBlurEffect(style: style)
            self.blurView = UIVisualEffectView(effect: blurEffect)
            let vibrancyEffect = UIVibrancyEffect(blurEffect: blurEffect)
            self.vibrancyView = UIVisualEffectView(effect: vibrancyEffect)
            self.sideContainerView.insertSubview(self.blurView!, at: 0)
            self.pinIntoSideContainer(view: self.blurView!)
            self.addChildViewController(self.sideController)
            self.blurView?.contentView.addSubview(self.vibrancyView!)
            self.pinIntoSuperView(view: self.vibrancyView!)
            self.vibrancyView?.contentView.addSubview(self.sideController.view)
            self.pinIntoSuperView(view: self.sideController.view)
            self.sideController.didMove(toParentViewController: self)
        case let .opaque(color, shadow):
