Trine 2 pre-orders have now begun on Steam, bringing with them an exciting bonus--instant access to the online co-op multiplayer beta. The new Steam product page also gives a December release window, the most specific we've seen so far.

Pre-order Trine 2 on Steam for $14.99 to get into the beta, which contains two levels of physics-based platforming fun. There are also "a few very cool TF2 hats coming as pre-order bonuses," Frozenbyte CEO Lauri Hyvärinen has teased.

Trine 2 is slated for a downloadable release simultaneously on PC, Mac, Xbox 360, and PlayStation 3, with a Linux version to follow later. The PC and Mac versions are SteamPlay titles, so buying one gets you the other too.

Frozenbyte "will most likely release at least one DLC campaign," according to Frozenbyte VP Joel Kinnunen. That's very tentatively penciled in for spring 2012, though Kinnunen says, "We'll know more after the game is out and we see all the feedback."