Portal 2: Perpetual Testing Initiative Co-op

Valve has updated the Portal 2 Perpetual Testing Initiative today, allowing users to create co-op levels. Map makers have already used the editor to make more than 170,000 levels. They have also added a "Quick Play" feature that creates never-ending, auto-generated playlists of the top-rated maps in a variety of categories. It has literally never been easier to figuratively jump in and literally play some Portal.

To celebrate the announcement, Valve is giving every Portal 2 owner a coupon to give to a Steam friend, netting them 75% off their own copy of Portal 2. This news also comes alongside the announcement of the new Steam Community features, as well as the co-op update to Team Fortress 2.