The idea is simple, but the game is very polished considering the short timeframe!
I love the soomth aniamtions, the screenshake, the hits feel impactful, the controls feel responsive. The menu looks nice with the animated title and button sounds.
The artstyle is cute and consistent, the enemies are pretty unique too, I got surprised quite a few times!
I do think the boss could have been made a bit more interesting because once you've killed the smaller butterflies in one go the big one just has a lot of HP and one heavily telegraphed attack. Maybe give it a more complicated attack once all butterflies have been killed. Then again, with only one hit point, the game can be quite difficult as is already.