This game is really neat, I like the glowing colors, and I appreciate that there is a health system. One tip that might help make a small improvement is: when an enemy is shot, you can pause for an instant on the single frame. GMTK often mentions that technique in his videos -- it really lets the play know they scored a hit, and it lets you reduce the screen shake a little bit too.
Anyway, this is still a cool game. You seem like you know how to develop and execute on an idea so I hope you consider my feedback!