You did really great with this game. The music, art, and just overall aesthetic are really well done. Having the cube being gelatinous really expresses the character well. I wasn't too sure about the game fitting the theme, but crossing and or combining mechanics (to "join together") did cross my mind. My main feedback would be to work on the controls a bit more. The rope felt a bit challenging to use. I believe if the rope controls were either more sensitive or switched to purely by mouse, it may work better. You could also allow the player to decide the sensitivity and or the controls.
I also did face a bug where the player got stuck on a lava/fire area where the player couldn't move or escape, and I had to wait until I died.
But overall, again really nice job.