Super cool idea.
Looping between characters inside a level that is also looping between other levels is something else.
I think it could use some music tho, something calm so it doesn't get annoying while solving the puzzles, I got quite tired of listening to the same jump sound effect over and over.
Also, sometimes the characters are not doing exactly what I did when controlling them in the previous loops, like missing a jump, or even straight up walking away for some reason.
Nice game regardless, good job !