private var pulseLayer: CALayer!

pulseLayer = CALayer()
pulseLayer.opacity = 0
pulseLayer.backgroundColor = outColor
pulseLayer.contentsScale = UIScreen.main.scale
pulseLayer.bounds.size = CGSize(width: maxRadius * 2, height: maxRadius * 2)
pulseLayer.cornerRadius = maxRadius
addSublayer(pulseLayer)

// The number of copies to create, including the source layers
instanceCount
// Specifies the delay, in seconds, between replicated copies
instanceDelay

// Determines the number of times the animation will repeat
repeatCount = MAXFLOAT

let scaleAnimation = CABasicAnimation(keyPath: "transform.scale.xy")
scaleAnimation.duration = animationDuration

let opacityAnimation = CABasicAnimation(keyPath: "opacity")
opacityAnimation.duration = animationDuration

let colorAnimation = CABasicAnimation(keyPath: "backgroundColor")
colorAnimation.duration = animationDuration

switch pulseOrientation {
case .out:
  scaleAnimation.fromValue = minRadius / maxRadius
  scaleAnimation.toValue = 1
  
  opacityAnimation.fromValue = maxAlpha
  opacityAnimation.toValue = minAlpha
  
  colorAnimation.fromValue = inColor
  colorAnimation.toValue = outColor
  
case .in:
  scaleAnimation.fromValue = 1
  scaleAnimation.toValue = minRadius / maxRadius
  
  opacityAnimation.fromValue = minAlpha
  opacityAnimation.toValue = maxAlpha
  
  colorAnimation.fromValue = outColor
  colorAnimation.toValue = inColor
}

let animationGroup = CAAnimationGroup()
animationGroup.duration = animationDuration + animationInterval
animationGroup.animations = [scaleAnimation, opacityAnimation, colorAnimation]
animationGroup.repeatCount = repeatCount
pulseLayer.add(animationGroup, forKey: kPulseAnimationKey)