126 Castaways on island eat unknown vegetation and become strangely transformed.
I'm thinking of this one as a simple RPG with an Oregon Trail kind of style. Manage your supplies of good food; trawl the ship's wreckage for barrels of salted meat or oatmeal, or hunt rats for meagre scraps. Try to eat as little of the vegetation as possible, or else the madness will take you as it has taken your now-monstrous crewmates. Defend yourself from them, bizarre and transformed. Explore the ancient cyclopean ruins that litter the island. Build a signal fire to attract rescuers.
I'm going to be trying not to spend too much time on this because I have a lot of work to get done this month as well, so it's probably not going to be terribly complicated. We will see.