Fantastic game - I love the soundtrack, it adds so much to the intensity of the experience!
Gameplay is challenging, but in a way that never felt unfair. Always got a soft spot for bullet hell games :) Once I followed your suggestion and started playing it like a rhythm game I found I took way less damage.
I love your solution to traditional HUD elements taking up space - the single pixel border as health indicator works really well, and makes for a brilliant way to get the most out of the 64x64 maximum.