Lot's of changes - the complete implementation of the Swift tutorials found here: http://www.raywenderlich.com/84434/sprite-kit-swift-tutorial-beginners  You can review, but I'd recommend going through it yourself.  I gained at least a top level understanding of what is going even though there's no way in Hades I'd be able to replicate this on my own without at least a week of practice.  Up next... Pong!