As usual, really awesome!
The art was easy on the eye, and the concept and execution were cool :)
With that said, nothing is perfect, and I have some feedback:
1. like others said, it didn't feel great that only one character could jump, but I completely understand why, as it's like the whole point of the game.
2. I personally would've preferred either clicking on the character you want to switch to, or just having one key to cycle, because I often cycled to the character that had beat the level.
3. when characters go off-screen, I wish that the camera would expand so that all of the players are in the frame
Other than that, really nice job!