Somewhere in the future, a planet called Sera has been overrun by subterranean creatures called the Locust Horde. You play as human survivor and ex-military grunt Marcus Fenix, imprisoned for "dereliction of duty" after abandoning your post in an attempt to save your father's life. As the game opens in your prison cell, the Locust Horde are advancing and the Coalition of Ordered Governments (COG) are low on conscripts. Thus you're pardoned and set free to stave off the Horde, and you must eventually lead Delta Squad through a series of missions aimed at destroying the invaders altogether.

Gears of War is a tactical third-person shooter similar to Ubisoft's Ghost Recon Advanced Warfighter, where progress through focused, restrictive levels is measured in judicious sprints as opposed to wild carnage-driven marathon runs. The camera hovers slightly above and behind you and can be zoomed by holding the left trigger button to aim any of the four weapons you're capable of simultaneously toting. Weapons themselves range from pistols, rifles and grenades to the powerful "Hammer of Dawn," which can drop particle beams via satellite relay on enemies if you have line of sight and open sky. Movement is tactical in nature, and you have several cover-related actions available, from ducking behind or mantling over barricades and debris to SWAT turns that let you hustle rapidly between adjacent cover points.

Multiplayer options include play online via Xbox Live and co-op play. It's possible to invite friends into single-player games and dynamically continue the story (the second player enters as Fenix's best friend Dominic "Dom" Santiago). Multiplayer game types include "warzone," in which a human fire team skirmishes with a Locust fire team; "assassination," where the goal is to off the opposing team's leader (Locust or human); and "execution," in which killing players after knocking them down requires special close-range kills.

Skip solo mode and go straight for co-op

For all its hype about "memorable moments" and "cinematic scope," Gears of War's single-player campaign turns out to be pretty paint-by-numbers. You sprint between furnished heaps of slag and concrete chunks planted precisely betwixt the impenetrable bounds of long, linear chutes. You hunker in the intervals between enemy gun bursts, intermittently probing for creature spawn points or scanning distant cover for possible head shots. You lean around corners, drop-roll between parallel cover points, slide unceremoniously along pockmarked walls, man shooting-gallery machine guns, pilot floaty monster trucks down cramped byways and trip invisible wires to cue canned skirmishes.

In other words, it's like most first-person shooters except for its superior visuals and a few pseudo-tactical moves. Think Ghost Recon meets Warhammer 40k with neither the former's tactical versatility nor the latter's more engaging background. Most of what's appreciable about Gears, rather, is how good it looks. That's its hook: environs shellacked with industrial grime and hyperbolic effects so bright and shiny it's like falling into the middle of a grungy geode. If you're into exceptionally good-looking games with toss-away stories, minimal character development and shoot mechanics lifted pretty much wholesale from classic franchises, Gears fits the bill.

Here's what doesn't: enemy AI that crouches behind pillars and barriers but dances ignorantly between cover and never seems to know whether (or how) to flank without scripted attaboys. Levels that appear broad and open use common hedge tools (blocked openings, unresponsive doors) to herd you along, and even the one or two "alternate" paths per episode are so obviously designed to bring you perpendicular to your opponent for easy kills that it's actually more interesting to wage head-on assaults. And because nine-tenths of the gameplay is sprinting, diving, crouching and mantling, it becomes all too easy to inadvertently get "stuck" against a wall. Half the game involves mastering the stick/unstick convention, and even then you'll be reloading like gangbusters because Fenix dug in when he should have dived. Worst of all, the game ships with a pretty humdinger bug: squad members that get "stuck" and refuse to regroup when ordered (the "fix" is to move forward, at which point they simply "pop" in behind you).

I could go on (my list of nits is longer), but OK, I'll give Gears this much, and it's why the game deserves good marks instead of merely mediocre ones: co-op mode. If you like to play alone, Gears is an AI drag, but play with a friend who can trade cover fire or help you flank with pizzazz and it's a completely different and more thoughtful experience. If you're looking for the summary turn-phrase, in fact, it's just three simple words: multiplayer or bust.