I liked the bosses they were a nice addition I felt like they came in too late in the game and my form was so strong at that point that they weren't really a problem. the only nitpick I can think of is that it wasn't clear what the stats upgrades would do for example I thought that increasing the attack speed would reduce the cooldown between attacks and not make the attack move faster. maybe you can add a more in-depth explanation when hovering over the upgrade. but really as a jam game, it is as good as it gets: cute idea, good art direction, and solid polish what more do you need from a jam game.
And the game was running well when I used Chromium instead of Firefox.