One small thing I'd suggest is that instead of using a realtime timer (eg 4 minutes, 3 minutes, 2 minutes et cetera) use a "clock" that goes up in hours (eg 11 PM to 12 AM to 1 AM et cetera ). An ingame clock representing real time would help alot with the atmosphere I'd think, and you can say the objective is "survive the night" instead of "survive 5 minutes" even if the duration that you need to survive stays the same.