Playfic is a website dedicated to creating "games" around pieces of fiction. The purpose is to allow users to write, remix, share, and play interactive text-based games with the world. Signing up for Playfic requires logging in to use the service. All the usual requirements to create an account are necessary. Want to learn more, check out this Playfic Tutorial to see a sample. If you want to learn more, check out this cheat sheet that explains how to play the game. Playfic uses a programming language called Inform 7. To learn more, click here.
I got to say that I think this is a great way to get students engaged in writing fiction, or for that matter playing games relating to fiction. It keeps the writing interesting, and catches peoples need for mystery.