Bullet Heaven is such a smart genre to do when constrained on inputs. Has the same kind of dopamine rush as vampire survivors.
Music is amazing! Title screen in particular had music so good I had to wait to start the game I was grooving too much.
Small nitpicks would be that sound effects could use a bit more juice / variation / tweaking, espeically when you're hearing the same sound effects constantly.
Lots of small details which really give it the "gameboy charm". Excellent stuff.