Starting on April 1, Valve released The Potato Sack {link no longer active} a one-of-a-kind limited-time crossover sleuthing event that brought 13 hit indie games together in one pack. Cryptic clues were dropped into games like Team Fortress 2, Half-Life, Left 4 Dead, Super Meat Boy, Amnesia: The Dark Descent and AudioSurf. Each clue had a common thread: Potatoes. A complex ARG (alternate reality game) glyphs or codes and hidden messages were slipped into each game, some were messages buried in simple text files while other games had all-new levels based on potato themes (Super Potato Boy became playable in Super Meat Boy). An all-new potato hat  {link no longer active} was unlocked for players of Team Fortress 2. Decoded phrases like “You found many. Find the rest.” and “Here’s Da Beens, Dougtato were also discovered in promotional videos {link no longer active}. A wiki called PotatosFoolsDay kept track of the game in progress. Players that unlocked all 13 clues get the game unlocked early on Steam and also get a special skin for Portal 2 co-op play.