You (Paul) woke up one day to find the world in shambles--everyone but you has disappeared. You have no idea what happened, as there's no one to ask---no people, no animals---but there are creatures that are attracted to the dark, so you must keep the lights on. The sun seem to be smaller, so days and especially nights are freezing, forcing you to use your heater that sucks up a good amount of power. Your last hope---a radio that lasts abut 5-7 minutes after its battery's been charged for 6 hours.
You've finally made contact with a girl, Elly, and only have a short amount to chat each day to maintain sanity. However, your makeshift generator is now left with only 30 kilowatt hours of power on its final tank of gas---running your heater 6 hours a day would mean it'd be dry in 5 days, and only two things can be plugged in at a time. You must balance running your heater, your microwave, your lights, and time on your radio and keep the unknown creatures at bay for as long as you can.
You may never find out why the world was laid to waste when you woke up, but you don't have to be alone.