Feels pretty good overall, very responsive movement and enemies line up in formations that make it very satisfying to mow them down.
However, there are a few pretty low effort things that you can do to improve the overall feel of the game and increase it's replay value (which is something you definitely need to do with a game this difficult since you're not going to learn the mechanics on a first run.
- make it so that you can respawn directly from the game over screen
- make it so that either the music does not stop between restarts or put more tracks in the game that randomize on restart so you don't have to hear the same 25 seconds (which is about how long I survive in this game tbh) of track over and over again
- more clearly communicate where the player's hitbox actually is, From what I can gather it's the torso, but it's really hard to tell exactly where it begins and ends and it's heard to wiggle through tight gaps in the bullet formations
- swap out some of the color pallete with colors that work better together from an aesthetic standpoint, I recommend using https://color.adobe.com/create or https://colormind.io to help you find good colors