This is really fun! Honestly, I'm not sure what I'd like to see improved on this, since it's already very well made. I think the only thing I don't really agree with is the decision to put the controllable character's health on the corner of the screen, instead of under the character like the other guy.
I had also encountered a bug where the uncontrollable character goes back and forth near the coin and doesn't collect it. Can't seem to reproduce the bug, though.