Wow, Im pleasently surprised by this concept. It was hard to grasp at first since there is no tutorial, but after I looked at it, it clicked and it suddently made sense!
With a bit of tweaking, you could turn this into a real nice puzzle platformer, with mechanisms and other fun stuff!
The openess of the first level is nice, having to ways of compleating it tells me there might have been plans to feature multiple ending depending on weather you slip with your partner or not. I like to think that was it.
I have two issues with this: 1.- The jump sucks. I simply dont like holding to jump, I think it would be better if when you pressed it, it sent you jumping, and tghe longer you holded the button, the more you would jump. At least the should be how it works while you are splitted.
And the other issue I had was with the physics of the boxes, moving them was a whole ordeal and sometimes I would get stuck on them or in between them.
Overall, Its pretty good, it fits the theme well and I loved how the music splits into two melodies. I just wished the black and white melody were almost identical in the number of instruments. The black one feels sad and lonly, while the white one feels inspiring and joined. 4/5, keep up thje good work!