Portal 2 pre-orders have launched on Steam, Amazon and GameStop. Naturally, Steam only offers the PC version while eager fans can purchase the title for Xbox 360 and PlayStation 3 elsewhere. By pre-ordering, you'll save $5 on the full retail price of $49.99 or $59.99 in addition to receiving bonus goodies depending on where you order.

Along with a 10% discount, Steam is offering pre-launch customers a free copy of the original Portal (you can give the game to a friend if you already own it). Instead of the complimentary copy of Portal, GameStop shoppers will receive exclusive customized skins for the co-op bots Atlas and P-body. Meanwhile, Amazon simply offers $5 in store credit.

Portal 2 is slated for a North American debut on April 18 while Australians and Europeans will have to wait until April 21 and 22. In case you missed the news, Valve and Sony have partnered up to implement cross-platform multiplayer gaming on the PC and PlayStation 3, and PS3 users will receive a free SteamPlay copy to play on PC and Mac.

Valve believes Portal 2 is the best game it's ever developed and it has several new features including a co-op story, polished graphics, as well as new puzzle elements and characters. The sequel takes place three hundred years after the original but features the same main character, Chell, and the same dark-humored AI computer system, GLaDOS.