Yeah that part was supposed to be explained but unfortunately the colliders didn't work after I uploaded everything. I didn't have time to play test unfortunately (I was in germany when the jam started and ended up having only 4 days to work)
What was supposed to happen is the player lets the boss damage himself until all the hearts on top left go black, and then the entrance at the right opens (but sadly it doesn't)
Sorry for all of those problems and inconvinience, and thank you very much for trying my game out