The Master Chief is back. The cyborg super-soldier spent most of "Halo: Combat Evolved" running around in circles on a giant alien construct, but in this one he gets to pound ground on familiar territory - Earth.

"Halo 2" picks up a bit after the destruction of Halo, an artificial ring world created by a long-extinct alien species.

The massive artifact was a sort of space arboretum and research facility that housed a virulent alien parasite called the Flood, capable of taking over the bodies of living hosts and using their knowledge to cause all sorts of trouble.

But Halo was also a weapon, designed to starve the Flood of hosts by wiping out all sentient life within range. Seems like a backward idea. Why not just wipe out the Flood instead of leaving it around to be set loose by an overzealous alien confederation? Speaking of which, the Halo-worshipping Covenant makes its return here in a big way - by going after Earth.

The game opens with Master Chief and the daughter of his late commanding officer attending an award ceremony aboard an orbital defense platform above the Earth. Then a Covenant fleet shows up.

The platform comes under attack by a contingent of Covenant troops, which plant a bomb that the Chief sends right back. Then he heads planet-side to confront a curiously small invading force in the city of New Mombasa, and from there ... well, let's not give too much away. The story has plenty of twists and dramatic moments, and while it doesn't end after the last level so much as simply stop, it's a good sci-fi yarn.

Storytelling isn't the main thing here, though; blasting aliens is. And the Master Chief has more ways to do that than before.

For starters, he can use several new weapons, as well as most of the old ones. The first game's assault rifle has been replaced by a submachine gun, the powerful magnum's scope has been removed and a new burst-firing battle rifle has been introduced. The shotgun and sniper rifle are unchanged, and the rocket launcher has a new lock-on feature.

But the Covenant have new toys of their own. Aside from the original plasma pistols and rifles, and the target-seeking needler, "Halo 2" introduces the semiautomatic Covenant carbine, the long-range particle beam rifle, the rocket launcher-like fuel rod gun and the grenade-firing Brute Shot. The first game's powerful plasma sword returns, and this time players can use it. Both of the "Halo's" grenades make an encore, as well.

All the smaller weapons can now be dual-wielded, and there are may potent combinations.

The enemy can dual-wield as well, though, and they've got some new tricks - and allies. The weakling Grunts return, as do the shield-toting Jackals, the cunning Elites and the massive Hunters. They're joined by the flying Drones and the apelike, berserk Brutes. There are other foes to encounter as well, including a handful of boss battles.

There are several new vehicles, and a new way to attain them: From the right position, Master Chief can board a vehicle and oust its driver, taking the wheel for himself. But beware; the enemy can do the same.

All these new features are fun enough in the single-player campaign, but they're even more of a blast in the game's multiplayer modes, especially since the game supports Xbox Live.

Here the mechanics introduced in the campaign really come into play. The various combinations of weaponry and the tug-of-war matches over vehicles serve to deepen the game's tactical nuances.

The multiplayer arenas are varied and well-designed, as are the single-player stages. There's none of the first game's backtracking here, nor is there anything as crushingly repetitive as "Halo's" Library level, though some of the indoor locations do get a bit similar. The game is at its best when the player is outside, ducking for cover and leaping into and out of vehicles.

The music, sound effects and voice acting in "Halo 2" are all superb, and the game looks brilliant 95 percent of the time; its sci-fi landscapes are gorgeous enough to give a player pause. But every now and then the more-detailed textures take a little time to load in, leaving the game looking boxy and flat for a moment. It's a small thing, but noticeable, and it disrupts the otherwise fantastic vistas and firefights that the game offers.

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Halo 2

4 stars

SYSTEM: Microsoft Xbox

PUBLISHER: Microsoft

HOW MUCH: $49.99 ($44.99 for Collector's Edition)

AGE RATING: Mature