Valve has finally, officially announced Deadlock, in the most minimal way imaginable. The game now has a Steam page that lists Valve as its developer and publisher, and a simple notice:
Deadlock is in early development with lots of temporary art and experimental gameplay. Access is currently limited to friend invite via our playtesters.
Valve provides no other details, just an animated teaser image. (You can see a still screenshot of it above.) The system requirements only mention that the...