Wow! What a great game! Very beautiful, very inventive, and with boss battles that are all very different. I really had a great time playing this game :D
However, it took me a while to figure out how to make the second boss vulnerable. You really have to pay attention to his animation, otherwise you'll be trying endlessly to parry his blows.
And also, for a color-blind person like me, the distinction between red and blue wasn't always obvious (especially as you have to be reactive!) Anyway, I still managed, and that didn't spoil my fun :)
Well done!