Great little game, and it's always fun to see another NES submission. I managed to get all gems, woohoo!
I for one think the music and the little variations between the different layers is pretty cool, and being totally incompetent when it comes to making music, I thinl you did a great job making something relatively decent on the NES.
I also liked the character sprites, they were pretty cute. The BG tiles need a bit of work however.
Couple nitpicks though: For one, some of the tiles are hard to discern whether or not they're solid, so I often found myself trying to go somewhere that was solid. Secondly, there were a few minor glitches, such as jerky character movement and a frame of garbled screen (Gotta be careful with nametables when scrolling ;) ) - But that is understandable in a 48 hour game. Finally, as someone else pointed out, I didn't really see the theme until the very end with the creepier layers - it looked more like a parralel dimension thingy rather than going deeper and deeper.
Either way, a stellar submission (And I wouldn't be surprised if you got a better score than myself this time, we gotta compare our scores like we did in LD44 haha)