In case you haven’t been solving testing chambers incessantly since April, Valve’s offering a free reason to dust off your copy of Portal 2. A new DLC pack, titled “Peer Review,” is up for download now via Steam, Xbox Live, and PlayStation Network.

“Peer Review” expands Portal 2’s co-op mode with a new test track, once again pitting the adorable P-Body and Atlas against GLaDOS. The DLC also includes single player and co-op Challenge Modes, each with their own leaderboards.

As an added bonus, Valve has lowered the price of Portal 2 on Steam to $14.99 until Thursday. You can also purchase two copies for $27.49. Act quickly and grab a copy of one of the best games released this year.