Went nuts, went fast. Just as advertised!
General game feel: Feels pretty good overall! There are some small things I'd suggest. There currently isn't audio-visual feedback for things like hitting the enemies, or successfully slicing bullets - there's no "impact" sounds if that makes sense. That makes the attacks feel less weighty. The small touches like enemy spawn animations and muzzle flash do add a lot, and I think you could go even further here.
Game design: I like it. Took me a second to get a hang of things, but once I understood the concept, I was quickly switching back and forth between gun-world and sword-world, clearing bullets and sniping enemies when I could. Some more enemy variety could be fun in the long term, if you want to keep working at it. A more elaborate scoring system that rewards you for multi-kills could also be fun, I think that's common in bullet hell games. I like it as it is, though.
Difficulty: Seems about right, I think. I'm not good at this type of game but I was able to survive for a few minutes.