You’re one of the survivors of a plane/ship/whatever crash. The game starts with a random wreckage, all players wounded in different ways/scattered, and a new island to figure out.
You must try to survive. You have to balance thinking of yourself and helping the entire group. (Potentially players have a family or friends or some other randomly generated connection at the start.)
Gather food. Build huts and campfires. Explore the island, looking for resources, secrets, and most of all: a way to escape again.
(Inspired by “Lost”, obviously.)