just left feedback, but ill repeat it here in case you dont see it, im also adding more here
i would recommend making the bosses telegraph their attacks a bit more, as it is now its a bit unfair
there should be difficulty in the full release, 1 hp for hard 3 for medium and 5 for easy, that would make the game a bit more inviting for new players whilst letting better players challenge themselves
i would recommend adding descriptions for each upgrade, and put the joke at the bottom
i would also recommend making the tutorial explain how different notes effect each other, like how green makes it go faster/farther as well as how some enemies work
i also recommend making doors not close forever and adding a map, though this is least important to me
this is my recommendations as of now i may update later