Wow, this one is really great!
I will start by saying that I am writing this as I didn't beat any bosses, because of a few glicthes (I think it may be a browser issue), for example the little slimes being still alive in their last phase before dying, and softlocking you in a nonexistent boss animation, and the boss glitching into the ground after splitting and going outside the map.
The gameplay loop is really fun, and the mechanic of the rotation very well implemented. The color/rotation matching mechanics almost evolves into a rythm game sometimes, and this I enjoy very much. The controls are smooth and responsive, and each swing feels impactful and satisfying. The art is great and very cute!
I could see this game evolving further in the future! Its mechanics are simple and easy to learn, but to use it fully it needs timing and skill!
Will probably play it again to see if I can beat all bosses on the desktop version!
Edit: reached the second boss, parrying the sword slashes is really cool! Tho I think this becomes as simple as standing near the boss, waiting for it to attack, and attacking with the correct color. I also noticed something the second time I fought him, it seemed immortal (I hit him for 5 minutes but it didn't go into phase 2).