The Perpetual Testing Initiative is a level editing and sharing service for the PC and Mac versions of Portal 2, released by Valve on May 8th 2012. It is free for all who purchased Portal 2, and is included directly in the game.
Users can create levels, and play them, and also share them online for other players to play. The level editor features a simple interface, and the ability to test play the level. The story line, albeit simple, involves Cave Johnson, the test subjects of Aperture Science, and multiple universes.
