Games like this are one of the big reasons I love Game Jams. I usually don't play this genre of bullethells, probably just because I have never properly tried them, but Jams provide a great setting to dive into all sorts, and in this case I'm really glad I did.
Its tough, especially because I'm not practiced, but I definitely enjoyed the difficulty. It felt fair, and I kept retrying because of that. I loved the take on the theme, the retro style and art, and the music too. A great entry, really.
I'd be interested to see what direction you take it if you continue development after the Jam