From the introduction:
Shelter is a game of survival in a war torn city, you must build your shelter, gather food and water, whilst avoiding the daily threats the war has created. The game has rules for you to play in a fantasy city under siege, a modern city caught in the crossfire or a future city under alien occupation.
Rules for building equipment and trading, gathering resources and other survivors, protecting the shelter when your away and for finding larger shelters to hold more people and stuff. You can play to survive or to take from others.
Designed for short campaigns.