CircleToRectangle-Step-13.swift

func animate() {
  if shapes.count == 0 {
    generateShapes()
  }
  
  for i in 0..<shapes.count {
    let delay = (i % 2 == 0) ? Double(i+1)/5.5 : Double(i+1)/5.505
    shapes[i].animate(duration: 5.0, delay: delay)
  }
}