There aren’t too many details regarding this Portal 2 DLC — namely what types of puzzle mechanics Valve is exploring this time around — but we expect, if it’s anything like Portal 2, it to be tons of fun.

And not just that, Portal 2: Peer Review sees the return of GlaDOS, the masochist robot made famous by the Portal games. In what capacity she will be returning (speculation left out for fear of spoilers) is anybody’s guess, but we hope that her trademark style of humor can mesh well with the duo of Atlas and P-Body.

Here’s a brief blurb on the DLC:

But the free Portal 2 DLC isn’t the only good news for Portal fans. Just announced is a 50% off discount for the game, making it even cheaper for gamers to check out both Portal 2 and the DLC. The 50% off Portal 2 sale runs through Thursday on Steam, so act fast.

While it isn’t the same as giving the first Portal away for free, to be able to get not just the full main game — which includes both a compelling single player storyline and a robust co-op mode — is a deal that we recommend you don’t pass up.

The only real disappointing element of this DLC release is the lackluster single player offering. Sure, a challenge mode has been oft requested by fans of its implementation in the first Portal, but now that the possibility of a really intriguing story have been thrown into the mix, it makes simply “thinking with portals” not enough. Here’s hoping more DLC, single player DLC in fact, is on the way.

Have you had a chance to check out Portal 2: Peer Review? Would you like more co-op DLC or some support thrown singleplayer’s way?

Portal 2: Peer Review is available now, and free of charge, on the PS3, Xbox 360, and PC.