// Extension
func motionEffect(intensity: Int) {

// Set vertical effect
let verticalMotionEffect = UIInterpolatingMotionEffect(keyPath: "center.y", type: .tiltAlongVerticalAxis)

verticalMotionEffect.minimumRelativeValue = -intensity
verticalMotionEffect.maximumRelativeValue = intensity

// Set horizontal effect
let horizontalMotionEffect = UIInterpolatingMotionEffect(keyPath: "center.x",
type: .tiltAlongHorizontalAxis)

horizontalMotionEffect.minimumRelativeValue = -intensity
horizontalMotionEffect.maximumRelativeValue = intensity

// Create group to combine both
let group = UIMotionEffectGroup()
group.motionEffects = [horizontalMotionEffect, verticalMotionEffect]
addMotionEffect(group)
}