I love love love this mechanic. That being said, I'm not sure how much of this is inspired by Terry Cavangh, so I'm not sure if I should lump that praise onto you. I wasn't aware of the Halting Problem, but I do absolutely adore VVVVVV and other Cavangh games.
But it's such an original take on the Sokoban clone game. I love the fact that you can push blocks around corners, whereas in other Sokoban games you'd be stuck. I love the fact that you can push jelly back together after it's been split. The puzzles are interesting and creative, and show off interesting properties of the mechanic.
That being said, you definitely should have eased the player into it. Level 2 is way too hard for level 2, especially after level 1. The player isn't even aware blocks can split at that point. Maybe a better solution would have been to just have a small T shaped corridor with a block at the intersection point, and then the player in the middle edge and the goals at the other edges. That way the player can only split the block. Also, I didn't realize jelly could go back into each other until level 7, so before that I thought if I made too much jelly, I'd just be stuck.
Anyway, great concept, thank you for bringing The Halting Problem to my attention. If any of these ideas were originally yours, take the praise. Game looks great too.