cool concept, well polished and rounded. I liked playing it.
Here some ideas you could maybe work on:
I think the "fast" one could be a little faster or use the double jump ability for a dash would would add another layer.
I did not like how the projectiles felt. They were as fast as the "slow" guy, If they impacted I did not get feedback. A healthbar and an impact effect would improve it a lot.
I let my wife play it and she did not realize that she could not climb the blue walls which let her think it is a bug.
One thing I really want to point out because I loved it so much is that you were giving a path based on your actions. Thats a great detail which makes the game better.