A bullet hell shmup I created and released a few years back. It features a few levels ending with boss battles, and your ship is upgraded with abilities as you progress.
Mostly for educational purposes and you cannot really compile it as there is a lot of game engine code missing. But maybe you can learn something.

The gameplay is pretty frantic and a bit too chaotic at times. It is also a bit monotonous and after 4 levels not much new (besides some new enemies and bosses) happens, but some people enoyed it. Check out the boss battles trailer below and you get the general idea of the game.