Hey, I made this! It's a community for writing, sharing, and playing interactive fiction games (aka "text adventures") entirely from your browser, using a "natural language"-inspired language called Inform 7.
Inform 7, if you're not familiar with it, is a bizarre world-modeling language that's modeled on declarative English sentences. You can view the game source to see what I mean, or look at examples in the recipe book: http://inform7.com/learn/man/Rchap3.html
I wrote more about the site, along with some screenshots, over here: http://waxy.org/2012/02/introducing_playfic/
