Now we know what Valve was doing those six long years--it was designing the most visually arresting first-person shooter ever conceived. In a genre that emphasizes whiz-bang engine features and high frame rates while usually skimping on pure artistry, Half-Life 2 is the genre's breakout accomplishment, marrying revolutionary technology with the strongest conceptual design we've ever seen in this style of game. Finally, a developer has created a first-person shooter that is so interesting just to look at and explore, the game could almost get away with removing the shooting element altogether.

Valve let its production designers' imaginations run wild in creating the strikingly unique visual style of the game, and it's to their credit that, with the exception of a few returning characters and weapons, Half-Life 2 doesn't look a thing like the original game. The arid New Mexico expanses of the Black Mesa compound have given way to City 17's dilapidated Eastern European sprawl. The otherworldly alien menace of the first game has been replaced by the calculated, brutal oppression of the Combine, personified by the ubiquitous masked stormtroopers who enforce the rule of the interdimensional regime.

Half-Life 2 is a game of moments, and the finest of those moments are literally unlike anything we've ever seen in a first-person shooter. The first time you step outside Dr. Kleiner's lab and see the towering, otherworldly citadel on the horizon is one of those moments. So is the first time you see the massive, War of the Worlds-like strider stalking your comrades in the streets of the city. So, for that matter, are your first meetings with Barney, Alyx, Eli Vance, and the other comrades who will assist your desperate rebellion against the Combine. It's to the credit of Valve's programmers that the Source engine's facial and character animation systems are so advanced, but it's the artists who leveraged this technology to create not just scripted 3D constructs, but characters who emote in subtle and utterly lifelike ways.

Valve could have gotten lazy with Half-Life 2. We could be playing another game set in Black Mesa, killing the same aliens and talking to the same nameless scientists. It'd still sell; it'd still be called Half-Life. But the designers instead rose to the occasion, creating a visual masterpiece that's made a lasting impression not only on its genre, but also on gaming as a whole.