Fantastic pixel art. What's animated is animated really well.
Obviously, there's a lot of stuff that's missing. It's a shame you weren't able to get more implemented during the game jam. Hope you keep working on the game after the jam ends; it has a lot of potential.
It's pretty easy to push the box into the corner before you know what you're supposed to do with it. The save feature helped in that regard, but it would have been nice if there was some way to reset the box's position without restarting.
Having the camera go up with the player every time they jump is a little disorienting. If the player isn't landing on a higher platform, the camera shouldn't need to go up with them.