The Art of Portal 2 Author:Valve A thrilling look at one of the most popular video games ever! The Guardian said it was "an astonishing experience." GameSpy called it "a near-perfect example of what can happen when all of the elements of modern game design are combined to create a beautifully cohesive whole." Now, Valve and Dark Horse pull back the curtain to give you a backsta... more »ge tour of one of the most innovative video games of the decade! The Art of Portal 2 walks you through the visual evolution of the award-winning game, from concept to completion, with never-before-seen concept art and insights from the writers and artists behind the Portal series.« less