Well, the theme for the 48-hour contest was just announced! "Light & Darkness"... The one of the 5 themes that I didn't have an idea for (well, of the 3 not-garbage themes). So I brainstormed by butt completely off, and now I have no butt and an idea which is currently called Spooky Skyscraper, which I have change since that's just a venue change from Spooky Castle.
Here are the idea notes I wrote down for it:
You see the skyscraper with windows, 8x6. You have a fusebox with only 7 fuses. Rooms with the fuses are lit, others are dark. Monsters come up frmo the basement. People are in the rooms and can walk from room to room, but will only move about when it's light. When dark, they stand and shiver. Monsters only move in the dark. If they come across a person, they eat him. If you turn the lights on on a monster, he zips to a neighboring room. If all neighboring rooms are lit, he is fried by the light. More monsters come up all the time, play until you lose too many people. Maybe each level has N monsters and N people, and you have to avoid losing N people. Either kill all the monsters or hold out until morning.
So that's it... I don't know if it'll be remotely decent, but it's at least what I'm starting on. So far I have an entire black screen fully implemented! Darkness: check. More notes as appropriate.