Eidos has announced that Batman: Arkham Asylum has shipped 2.5 million units since launch.The game, recently released on PC and less recently released on PlayStation 3 and Xbox 360, has done well for itself with 2.5 million units having shipped to retail since it launched a few short weeks ago.It’s not surprising, either. The game – which sees Bats trying to regain control of asylum-prison Arkham Asylum from the Joker – is bloody brilliant. We, and it deserves every 0.1 of that score. This week, Bats was hanging around the in fourth place, but it’s good to see the sales still high.In other Batman news, those of you who have the game (quite a lot of you, by the sounds of it) can get your hands on the , which adds in a pair of free challenge maps to the game. Did we mention it’s free? As for those of you who don’t have it – well, if our review isn’t enough for some reason, then did you know it’s been awarded a ? It’s true.