I really like this game, I haven't played any bullet hell games before but this one is so cool.
I really like the healing mechanic, its easy to use when it's calm but when the screen is full of bullets it makes even more chaotic which is great. I like the way you can press space, then remember which key it is and then be able to quickly heal later. Not sure if that was intended but it's nice.
One thing I'd like is a pause screen.