Excellent work. One of the highlights of the games I played. I'll fully admit that I got frustrated pretty quickly, but that didn't lessen the memories that formed from me playing this game. There were many unique encounters and a gradual increase of the number of powers that you have. And to top it all off, I've never played a bullet hell like it! I'm super impressed.
I do think tweaking the numbers on any combination of gravity, enemy sphere radius, or enemy health regeneration to be kinder to the player would go a long way for me personally, without losing the fundamental experience. But that comes from iteration and feedback, and even with quitting, i had fun. Great job.