Apr 19, 2011 08:29 GMT  ·  By

Valve has announced that Portal 2 is now available worldwide. Mac gamers can sign in to Steam and download the game right now. Retailers are also preparing to sell the game as of today. The original Portal was named 2007's Game of the Year by no less than 30 publications across the world.

“Portal 2 is now available worldwide via Steam,” Valve said today. “Portal 2 draws from the award-winning formula of innovative gameplay, story, and music that earned the original Portal over 70 industry accolades and created a cult following.”

Building on the success of the original Portal, the sequel features not only a single-player game mode, but also a cooperative mode which features its own separate campaign with a unique story, test chambers, and two new player characters.

“Success will require them to not just act cooperatively, but to think cooperatively,” Valve said.

As for the single-player mode, it introduces new characters too, as well as fresh puzzle elements, and a much larger set of test chambers, something that will undoubtedly please those who believed the original Portal game was too short.

According to the developers, “Players will explore never-before-seen areas of the Aperture Science Labs and be reunited with GLaDOS, the occasionally murderous computer companion who guided them through the original game.”

Portal 2 also boasts some advanced physics which allowed Valve to create a whole new range of challenges.

This resulted in a much larger but not harder game, the makers stress.

Last, but not least, Portal 2 will have what Valve calls “editing tools.” These will be made available separately, after launch, Valve said.

Mac system requirements include Mac OS X 10.6.7 (Snow Leopard) or higher, an Intel Core Duo Processor (2GHz or better), 2GB of memory, at least 7.6 GB of hard disk space and one of the following video cards: ATI Radeon 2400 or higher / NVIDIA 8600M or higher / Intel HD Graphics 3000.

Visit Steam to start thinking with portals, again.