It all stated on the first of April when Steam released the "Potato Sack" Collection for PotatoFoolsDay. However in all the 13 games on the collection they released a small patch which changed some small files and added small new maps etc. Much like they did back last year when they added radios that played morse code and SSTV images. People haven't got very far deciphering everything yet so there's plenty of chances to help them out, or simply do what i do and sit back and watch the progress. Jump onto the Portal2 forum on steam and follow the threads for the fun, or simply keep track of the up to date wiki for the ongoing results.
Also The portal 2 release date was upped today on steam, unlocks on April 19th










