Incredibly unique ideas here! The concept of having to switch between bosses on the fly, rather than fight them sequentially, is an incredibly unique one. Unfortunately, I didn't find the gameplay to force the player into that mode of thinking as much as it could have. I found that the yellow, red, and blue bosses could all be defeated pretty easily by just strafing in a circle, and attempting to parry just opened me up to taking damage when I could usually avoid it. Making the timing of the parry a little more forgiving might help make it a more viable option. But there are so many cool ideas here, that I really hope you continue to iterate on it. Overall, great work!