Interesting game. The idea of being in one layer at a time is really cool !
However, there are stuff that you can improve for instance music was a bit loud and repetitive (I played on windows). The UI and game need polish overall but that's more a Jam issue with only 48 hours.
Switching layers with only the tab button can be a bit annoying. I understand this choice but I think putting the enemies layer just after the environment layer is a bit more logical since you are moving in the environment then you get hit and you can see directly what's attacking you by pressing tab once. In your game you have to go through all the layers to see the monster which can be a bit irritating.
I also think the pause layer is quite useless and getting rid of it wouldn't harm your game in my opinion. Imagine being a player and you need to pause the game quickly to do something else. In your game you have to go through the layers and stuff it can be annoying for the player. I think pausing the game should be a feature always accessible.
Finally the game is quite hard to understand at first. At the beginning, you are lost in all those layers without knowing what to do. For your future games try to make some kind of tutorial inside the game which shows and introduces the game mechanics one by one at the player.
I also saw some bugs like enemies being visible in environment layer or if you start the game and don't press tab at all you can see both the enemies and environment.
Anyway good stuff ! Congrats !