Core Graphics Tutorial Part 1: Getting Started

Hello,

Can someone elaborate on this single line? It’s the only one giving me fits because I’m not sure what angleDifference is meant to represent. Where does 2 * .pi come from?

let angleDifference: CGFloat = 2 * .pi - startAngle + endAngle

I can see that this is then used to divide up the gauge into 8 slices, and I’ve played around with 2 * .pi to see that changing it changes the width of the slice, but I’m still confused. Thanks!