Games to keep you awake

Hello all,

My situation basically is that I work in a care home, which means im stuck with crippling night shifts with only me and my laptop for company (but no internet access)

Normally I just TV/films when all the residents are sleeping, which unfortunately doesn't stop me from KO-ing during the night.

The only PC games i've got is a sega megadrive emulator, so my question is, can you guys recommend any PC games to keep my brain going at night (preferably one that doesn't require an internet connection)

all recommendations welcome.