Despite so much of the game's appeal coming from its free structure, there is plenty to experience with the boss battles. Nearly all of the boss compounds have been constructed and placed in such a way that there are multiple entry points and attack routes depending on your particular style of play. There is, of course, always a front door option that simply has you barging in guns blazing, battling through waves of gang members until reaching the boss' inner sanctum. A beach villa, however, might have an underground access tunnel reached via the ocean, while a boss residing at the top of a tall skyscraper might be accessible by scaling the building and climbing in from the roof rather than taking the stairs. Approaching each boss location, your deep voiced narrator--who, in true Xbox platform burly dude action game form, sounds like the Price is Right announcer version of Gears of War's Marcus Fenix, right down to spouting modern day frat boy exclamations like "Niiice"--will inform you whether you're likely to succeed at your level of ability, while a precise percentage rating appears on screen. I was once able to eliminate a boss after being given a 13% chance of success by jumping through his window, tossing down half a dozen grenades, and shooting off a rocket as I leapt out again. Good times.

In a nice touch, each gang's six sub-bosses control a particular supply chain for that gang--weapons, vehicles, new recruits, and so on. Taking out a boss will reduce a gang's effectiveness in the corresponding area. After taking out a gang's final kingpin and battling a last uprising, the district will become crime-free. Upon vanquishing all three gangs, you will be treated to a rather suspect and shoehorned-in cutscene (to cap off the story that never really existed in the first place), after which you are free to roam the city in peace, devoid of gang members. It's a somewhat surreal opportunity, and is a good opportunity to seek out lingering agility orbs and complete races on foot and by car, without being randomly harassed (except by the police when you accidentally run over dozens of pedestrians). Fortunately for the sake of wanton destruction, you can choose to turn on random crimes, which will restore gangster spawns to the streets. It is also possible to replay any of the game's boss missions in a time trial mode, which like races are tracked on online leaderboards.

As discerning gamers know, cooperative play makes everything better, so Realtime Worlds deserves credit for implementing the feature here. There's no same-screen co-op, but having the mode playable online through Xbox Live is highly appreciated. Due to its open structure, co-op in Crackdown is extremely straightforward: you both exist in the same city at the same time. That's about it. Obviously, most of the time you'll be helping one another out to achieve various goals, but there's no reason that need be the case unless you are playing a cooperative time trial. Speaking of that mode, the co-op time trial could use some work; upon completion of each mission, both players are kicked back to the front end menu, at which point the hosting player selects a new mission and waits for the other player to rejoin. A persistent lobby would have been useful.

I have never been particularly interested in Achievements on the Xbox 360, particularly in story-driven games. Crackdown, however, seems like the type of game for which the system was expressly crafted. With the skill system and the lack of a traditional mission structure, the much of the pleasure of the gameplay comes from pulling off amazing acts, and such acts are precisely what the game's Achievements reward. There are the expected standard milestones such as maxing out the various abilities and taking out each gang's string of bosses, but there are also Achievements for killing 200 gang members without dying, killing five gang members while airborne during a single jump, keeping a car in the air for six seconds using explosives, reaching the top of the staggeringly tall Agency Tower (and then another for jumping down), and so on. There is a good spread of Achievements that you are likely to acquire by using your skills to the fullest and Achievements that you will have to work to acquire. The latter includes long term goals such as finding all 500 agility orbs as well as frantic short term ones such as pulling off six car stunts in a minute. In a sense, the Achievements serve as ersatz missions, without having to work in any kind of context or plot.

There are some more minor odd niggles throughout. Targeting is likely to crop up as an issue from time to time, as for some reason the auto-lock occasionally decides you'd much rather be shooting that guy two blocks away instead of the one five feet in front of you. After the system has made up its mind, it can be difficult to make it reconsider in the heat of battle. There also seems to be an odd bug that sometimes causes highway traffic in a given direction to dissipate entirely until you look away and look back, at which point you will inexplicably see several cars that weren't there before, driving away from you. When you do happen to be stranded in the middle of a long bridge and need to go in a particular direction, this can be frustrating. It would also be nice to be able to kick in midair, a strange omission given the range of other tasks that can be performed while airborne.

In GTA, much of the initial non-narrative appeal stems from allowing the player to do fairly extraordinary things within a surprisingly rich and realistic world, at least compared to most video games. In Crackdown, much of that environmental richness is missing--there are really no characters in this game, no meaningful dialogue, nor a set of varied missions--but the sandbox elements are put in such a different context and played up to such an extreme degree that it really does become its own game. A GTA clone it will inevitably be called, but it also makes the strongest case yet for avoiding terms like "GTA clone." By going back to the drawing board with the fundamental elements that have made open world games such a prominent part of the gaming landscape, Realtime Worlds has managed to carve out a new segment that is both enormously compelling and unapologetically fun.