First off, music is immediately banger, great job on that~! Also main menu is super polished and the fact that you have one with settings is awesome!
I don't think I'd call the game a bullet hell though, it feels more like a shoot-em-up, I'm not quite sure why - maybe because there aren't that many bullets and they don't go off in all directions?
The screenshake is really neat, like quite subtle for small things yet with the potential for more shake, I like that~
There is so much to like about this game, the varied enemies and shots (bombs etc.), the funny death messages, the unknown cheat code entering~ very well done.
One thing I noticed is, there is never a reason not to shoot, so binding it to a button that functionally should be held at all times is kinda tedious. You could either always fire and not use a button for it, or have firing not be the optimal strategy all the time - like slowing you down while you're firing, or something like that~
All in all, a really solid entry - thank you for sharing this with the world :)