Nice game! With a tidbit of polish, I think you can go far with this concept. Here are my two cents:
- The controls are too sensitive, making it difficult to correctly land on a platform of 1 tile.
- The player should be able to use the rewind in case they fall in the pit.
- The pit in the entry level, after the mob, does not trigger death.
- In the underworld, you can get stuck under the falling block making it hard to rewind. Could be a bug, could be a feature ;).
- The enemy asset is clashing a bit with the feel of the game.
- It's not entirely clear that jumping onto an enemy kills it.
I hope my comment is not too overwhelming, I really think you got a good concept: it's working correctly and I like the art style.
Keep up the good work!