This includes (or will, when it's done) extensions from the textbook associated with the course, which take the prototype past where the course left off.
Some of the graphical assets used here are freely available at: http://kenney.nl/assets/puzzle-pack-2
"Popcorn Slider Loop" Kevin MacLeod (incompetech.com)
Dedicated to the Public Domain
Sound effects created at http://www.bfxr.net/