Pretty tough boss fight, but overall well made I would say.
I think some of the combat design choices were not standard for the genre. For example, usually when dashing or for a short time after being hit, the player would have a small window of invulnerability, but as far as I can tell there isn't one in this game, or maybe it's too short and it felt a bit unfair to play. If there was invulnerability, you should also add some visual indications for the player when he is invulnerable.
Sound is ok, but may feel a bit mismatched given the visuals.