This song is super catchy! I was playing the game that came along with it, and honestly it's the perfect tune for just vegging out and jumping over the tombstones for like an hour. One thing that impresses me especially is how you work in instruments with different quality levels into eachother. There is definitely some "realer" sounding instruments that are mixed in there, but they feel totally natural among all the 8-bit ones. This is great.
My main issue with this song however, is that I can't see how this would fit the boss battle theme.
Still, great job!