As a member of the outfit, you lead a four-man, AI-controlled squad that can be given attack and suppress orders, as well as special attacks specific to a character, like Tommy Mac's Gas Attack. Thanks to the variety of vehicles, emplacements and air strikes, the game never plays the same way twice. But it's far from open-ended in the GTA sense, and most single-player levels feel as ducted and walled in as a level of Quake. The best maps in the game are more like an open sandbox, allowing you to build up your defenses and strategize as if you were playing WarCraft II.
Of course, none of those constrictive levels are a problem with online multiplayer where the game starts to truly shine (single-player co-op on Live is a killer feature, too). Playing two-on-two multiplayer maps - where each player commands his own squad and builds his own equipment - offered some of the most fun we've had online in a long time.