Half-Life 2's presentation is extraordinary, thanks to the new Source engine. Even though Half-Life 2 debuted a year later than originally anticipated, it is still very much a cutting-edge game, featuring state-of-the-art graphics technology. While Doom 3 features superior lighting and shadowing, it didn't really succeed at bringing a credible and cohesive world to life. Half-Life 2 does, and the environments in the game are simply stunning, from the plazas and streets of City 17 to the rusted interiors of an abandoned factory. There's also some excellent level design in the game, including a deserted town full of deadly traps and the gaping interiors of an alien citadel. The engine does a great job of rendering both indoor and outdoor environments, and there's a lot of eye candy to absorb if you have the hardware to handle it. Most surfaces nearly glisten with the latest shader effects, and the textures are sharp and richly detailed.

One of the big new features is the incorporation of physics into the engine, and that has an effect on the visuals as well. Basically, everything moves and behaves as it ought to, so when you hammer a strider or a gunship with a rocket, it shudders and recoils from the impact. Characters also move in a lifelike manner, and the animations are smooth and believable. You'll also discover that objects in the environment can be used against you--there's nothing that zombies like more than to hurl a metal barrel in your direction. On the other hand, you can use the gravity gun to hurl objects about, or even to pick things up and use them as a shield.