The single-player campaign in Killzone is spread across 11 missions, each broken up into multiple parts, and it basically pits you against legions of Helghast soldiers in many different environments. You'll travel from a bombed-out city to an industrial-docks area, from the jungle to the desert, from a snowy mountain region to an orbital defense platform that's key to the Helghast invasion strategy. So yes, there's a lot of variety in the game's backdrops. Unfortunately, there's not such a great range of enemies to fight. The vast majority of your opponents are basic Helghast grunts, occasionally joined by other Helghast grunts who look slightly different and fight with shotguns or rocket launchers rather than the standard-issue assault rifle. This sameness in enemy design isn't utterly damning but doesn't really do much to enliven the action, either.

The game's combat, ostensibly its biggest selling point, can be exciting at times. Sort of. Occasionally you'll get to take on a tank with a rocket launcher, repel a beach assault from a fortified position, or perform some other unique, mission-specific action. More often it's simply running from point A to point B, firing at every Helghast in sight until you hit the right switch, blow up the right box, or reach the right area to advance the mission to the next event. The arsenal–which includes assault rifles, a sniper rifle, a shotgun, a vehicle-killing rocket launcher, grenades, and other genre mainstays–doesn't really pack much of a punch. The shotgun, with its horribly slow rate of fire, is rather ineffectual; the sniper rifle's aiming system is too loose; and the assault rifles are only sporadically accurate (and while this inaccuracy might be realistic, it isn't particularly satisfying). The guns do their killing properly but with little panache.