It was a difficult but fun boss battle!
The weapon that returns to your character felt unnecessary because the throwing and return speed was slow, and combined with the boss's fast movements, I was never able to hit the boss's back eye when it returned.
So, right now, I only feel that the return element is a bit annoying.
Maybe if different bosses are added in the future, that action aspect will become important.
The boss's fatal attacks can only be dodged perfectly, so I was getting killed a lot at first, which was tough.
It would be nice to have a guard when holding a weapon. If guarding meant you'd stagger for a while after taking an enemy attack, but it would be safer than dodging and neutralize the attack, which would make it easier to learn the timing for dodging.
But even the first boss was plenty of fun!