This is a simple game engine started from one of my class. But I push much much more efforts on it. It contains the topics of D3D9/OpenGL rendering, cross platform, asset tools, collision detection...
I develop this so that I can have a better understand of technologies we're using everyday. The structure is very similar to Unity3D.
BTW, just started to work on GitHub, so if I missed anything from you please send me message :-).