Function for controlling button's shadow based on input force

ForceButton.swift

    func shadowWithAmount(amount: CGFloat) {
        self.layer.shadowColor = shadowColor.CGColor
        self.layer.shadowOpacity = shadowOpacity
        let widthFactor = maxShadowOffset.width/maxForceValue
        let heightFactor = maxShadowOffset.height/maxForceValue
        self.layer.shadowOffset = CGSize(width: maxShadowOffset.width - amount * widthFactor, height: maxShadowOffset.height - amount * heightFactor)
        self.layer.shadowRadius = maxShadowRadius - amount
    }