Really fun. I liked the variance in attacks, which is one of the things I think makes for a good bossfight. A lot of the attacks also just looked pretty cool, like the one where the heart pieces come together in phase 2. I liked how the eye kept changing places so you had to track where to shoot him in the first phase, and I almost wish there was something like that kept for the second phase. Also, the W key doesn't really work as a jump key, I think that may be a bug.