There seems to be a major game breaking bug on level 3 that makes it impossible for me to properly control the characters after dying on the acid. Nevertheless,
The good things:
Simple execution means simple tutorial means its easy to teach the concept to any other players.
Major caveats:
With the way the game is designed, you have seperate levels for each of the 2 knights which leads to instances where I basically focus on one player only and ignore the other which can defeat the purpose of the joint mechanic.
But you've definitely gone down the right path initially. I am softlocked behind level 3 so I can't past beyond that to give more critisms.