Zombusters is a commercial game which released the code and assets. It is a zombie twin stick shooter. Unfortunately I found it kinda boring. The waves seem like the same thing over and over again. They are time consuming but not hard. New enemies are very slowly introduced. Steam page says there are multiple weapons but I never saw any. It also doesn't handle full screen properly. I think the mouse controls are off even in windowed mode. Controller works except I couldn't increase the starting level. I got to level 2 so I think it should be available but maybe it is only available when you beat the level.