     private let internalStackView = UIStackView()
     private let buttonStackView = UIStackView()
     private var blurredBackground: UIVisualEffectView!
+    private var vibrancyView: UIVisualEffectView!
     
     
     // MARK: - Constants
     
     private let maxWidth: CGFloat = 350.0
+    private let minWidth: CGFloat = 280.0
     private let outerMargin: CGFloat = 6.0
     private let internalMargin: CGFloat = 6.0
     private let buttonHeight: CGFloat = 44.0

        titleLabel.textColor = titleTextColor
        updateButtonColors(buttonOne)
        updateButtonColors(buttonTwo)
        blurredBackground.effect = UIBlurEffect(style: lightBackground ? .Light : .Dark)
    }
    
    private func updateButtonColors(button: UIButton) {

        mainStackView.topAnchor.constraintEqualToAnchor(blurredBackground.topAnchor, constant: outerMargin).active = true
        mainStackView.bottomAnchor.constraintEqualToAnchor(blurredBackground.bottomAnchor, constant: -outerMargin).active = true
        mainStackView.widthAnchor.constraintLessThanOrEqualToConstant(maxWidth).active = true
        mainStackView.widthAnchor.constraintGreaterThanOrEqualToConstant(minWidth).active = true
        mainStackView.centerXAnchor.constraintEqualToAnchor(blurredBackground.centerXAnchor).active = true
        
        mainStackView.spacing = internalMargin
        mainStackView.axis = .Vertical
        
        let vibrancyEffect = UIVibrancyEffect(forBlurEffect: blurEffect)
        vibrancyView = UIVisualEffectView(effect: vibrancyEffect)
        mainStackView.addArrangedSubview(vibrancyView)
        titleLabel.translatesAutoresizingMaskIntoConstraints = false
        vibrancyView.contentView.addSubview(titleLabel)

        titleLabel.leadingAnchor.constraintEqualToAnchor(vibrancyView.contentView.leadingAnchor).active = true
        titleLabel.topAnchor.constraintEqualToAnchor(vibrancyView.contentView.topAnchor, constant: internalMargin).active = true
        titleLabel.trailingAnchor.constraintEqualToAnchor(vibrancyView.contentView.trailingAnchor).active = true
        titleLabel.bottomAnchor.constraintEqualToAnchor(vibrancyView.contentView.bottomAnchor, constant: -internalMargin).active = true
        
        titleLabel.numberOfLines = 0
        titleLabel.textAlignment = .Center
        titleLabel.setContentHuggingPriority(UILayoutPriorityRequired, forAxis: .Vertical)
        titleLabel.text = "Are you happy with this app?"
        
        mainStackView.addArrangedSubview(internalStackView)
