I like the character merging aspect where only red can jump and green can attack!
Your camera controls are incredibly oversensitive, I found steering the camera the hardest part of the game!
I also found your combat a bit dull: Fighting enemies takes too long and locks your movement/position for a good while. I ended up bouncing on the enemy heads to get up on the walls for the last couple levels just to speed things along!
It took me a while to find the key control for rejoining (2), putting the key prompt in the join together text box would fix that issue right away.
Thanks for sharing this!