Jump, Toby! Jump! is a Jump'n'Run Android 2.1 game (or rather demo) I programmed in 2013. I made horrible design decisions (especially concerning the main loop) and the OpenGL stuff is crap (there're so many avoidable drawcalls), it's a miracle the game runs on my 2009 phone.
But of all games I programmed I learned the most from this little Jump'n'Run.