Nice game!
Having friendly fire is a creative choice, it's not often in games that there are hazards for both you and the enemies, or maybe I just haven't seen it because I don't play much games :p, either way, it makes for a challenging twist.
So, I did notice that the characters are not visible in the character select menus, perhaps you intended to place their portraits there? If it's not a bug, maybe the in-game sprites could serve as a good placeholder.
I think it would be convenient to be able to read the description of an ability from the pause menu, it took me a while to figure out how the portal gun works.
Overall, this was a fun experience!