Pretty enjoyable game! Movement and the mechanics you get as progression felt good for the small screens. I liked how it looks too. I managed to get to the top and finish it.
I do think it could have used a couple more markers/extra decorations to keep some rooms a bit distinct, even being a pretty small map, at the start I kept getting mixed up where to go and retreading the same path.
Some nitpicks I have, besides some bugs (I kept getting freezed even after getting the coat upgrade, wall jump would sometimes not work):
- the spikes hurtbox felt a little bit too big, in some cases the character wouldn't be touching it and it would be a hit. I think giving a pixel or 2 of leeway before getting hit would make it feel a lot better.
- the checkpoints were very inconsistent. whenever I died I would never be sure where I would respawn. maybe having set checkpoints, or more consistent rules of when they were being set would be better (maybe how they were being set was a bug too?, sometimes I would be standing in a very safe spot, die, and be sent back to the previous area).