public class ZeroConstraint: NSLayoutConstraint {

    public override var constant: CGFloat {
        get {
            let adjustedConstraint = super.constant * SizeAdjustment.percentage
            return adjustedConstraint
        }
        set { super.constant = newValue }
    }
}

struct SizeAdjustment {

    // The percentage each element should scale by
    static var percentage: CGFloat = {
        // We design everything at this width (iPhone X). Scale up or down in
        // relation to it.
        let baseWidth: CGFloat = 375.0
        let percentage = UIScreen.main.bounds.width / baseWidth
        return percentage
    }()
}