The controls of this game are interesting because of the way the characters are joined together. I like how the players need to cooperate with each other to proceed but their controls are flipped so trying to move normally itself is a challenge.
I think one major improvement that can be made is the addition of checkpoints. I know this was said from others but I'm also going to chime in on this as well since your game is pretty lengthy from what I remember. Having those checkpoints can really keep your players motivated since they won't have to restart the entire game upon losing.
Great game! Glad to see it make it to this point!