Cool boss design and behavior. Pretty clean design, and the exchange mechanic is really cool. I didn't manage to defeat the boss, but that's a problem of my skill and I think I would manage it, when trying more often. We did a platformer too and I really appreciate your smooth character controller. I'd like to try the controller out more and see how he behaves, but then this boss comes and interrupts me :-)
Everything leaves a lot of room for expansions.
Good job