I've bought a mac mini with macos x "El Capitan" on it to write some Apple Source Licensed software.
The Open Source License of Apple Computers. It's made in the latest XCode (IDE) from the Apple Store (XCode is free.)

Thing is I started out on an adventure game kit, so with single non-moving backgrounds. There's also
entity game objects and a timered (NSTimer) move algorithm.

It's complete to start hacking further on it except maybe for an NSTimer in the mainGameLoop.

The source code can be found under the name "The Legend of Uldramar" at
http://brandywine-software.yellowcouch.org/macosx/

Enjoy!