The original Portal had the element of surprise. Its style of first-person physics-based puzzle game play was unique. Glads, the murderous robotic villain, was new and vibrant and evil in the most charming way. Cake jokes and songs about surviving dismemberment were still hilarious. It was short, succinct and essential. Creating a sequel without playing all the same notes and making it feel like Portal: The Longer Version is a tough task. For Valve, it's apparently no problem.

From the first moments of waking up in the rusting Aperture Science facility to right before the credits roll, Portal 2 rarely falters. The world is bigger, the story thicker, and the character development more surprising. The mania of Glads, the facility's operator, is molded into unexpected forms alongside a host of brutally funny personalities. The history of the Aperture Science facility is filled in, character origins discussed, and though its pacing suffers as it occasionally strikes a more serious tone,