This demo was created to help support one of my CocoaConf talks. The demo shows various techniques for building an interactive, animatable pie chart using Core Animation (CAShapeLayer, CATextLayer, CADisplayLink, etc.) At the root of the solution is using a dynamic CALayer property to control the custom animations. The same technique can be applied to other solutions. The view uses a data source (number of slices, slice value) and delegate (selection tracking).