Sometime after the release of Grand Theft Auto III, the popular term used in the game industry to describe open-world, mission-based games became "sandbox." It's kind of a dopey term, but it makes sense and properly conveys the sense of freedom that these games tend to have. But even with the freedom offered by this style of game, most of them tend to have a pretty rigid structure for you to follow if you want to see the game through to its storyline conclusion. Crackdown, from Microsoft and Real Time Worlds, tends to get away from that aspect. The result is an open-world game that feels more open ended than any other game of its type, but that lack of structure makes the game feel half finished and shallow in a few spots.

As you increase your abilities, your character will appear to age.

There's a bit of backstory to the action in Crackdown, but all you really need to know is that you're a new type of supercop that can evolve very quickly, which means your skills improve as you play. You're out to clean up the streets. There are three gangs, each with seven leaders. You can take on any gang leader at any time, but there's a logical order laid out for you that makes the progression scale as your skills increase. There isn't much difference between each individual gang leader--you just need to get to where that gang head is by either working your way through, around, or over the gangsters that surround the leader, then open fire on the boss and take him or her down. Once you eliminate all seven leaders of a gang, a "final crime" occurs, which is really just a mess of street soldiers wandering around in one specific area. When you take all of them out, the gang is vanquished and you'll no longer run into any resistance in that part of the city. Once you've repeated this process through all three parts of the city, you're done cleaning up the city. It's got an abrupt and disappointing conclusion, overall. But before you can have a plot twist, you have to have a plot, and Crackdown has neither.

The weird part is that none of the story really matters, because the whole point of the game is to provide open-ended freedom and a large, interesting city to explore. And on the gameplay side, Crackdown works. The city might not seem huge when you first start moving around, but that's more because you're not thinking vertically. As a man with superhuman abilities, you'll get stronger, faster, and more powerful as you play. The plainest representation of this is your agility rating, which you increase by collecting orbs that are hidden around the city on rooftops. As your agility increases, you can jump higher. So what initially seems like a high, but unimpressive, jump at the beginning turns to your agent flinging himself through the air, from one rooftop to the next, or scaling buildings by clinging to window ledges and jumping up the side. The range of movement you get once your agility is up is really impressive and makes moving around the world a lot of fun. Also, firing from the rooftops or jumping in on your enemies from above is a great way to clean up the opposing gangs, so it's got tactical considerations, as well.

While gaining agility is dependant on collecting orbs, the rest of your skills increase by simply using those skills a lot. You'll earn skill in firearms for shooting enemies, and as it increases, the lock-on targeting system becomes faster and more effective, though it can still be a bit touchy, even when you're at the maximum level. The strength skill increases when you kill enemies with melee attacks. Increasing your strength gives you more health, and, well, you're stronger. When you're pumped up all the way, you can kick cars and they'll go flying. You can also pick up vehicles and jump around with them or throw them, which is often fun. You earn driving points by performing stunts in your car or by running over enemies. As you level up your driving, car handling and speed improves, and special agency vehicles that you can request back at headquarters change shape when you get in them, becoming more effective in the process. When you get a four-star driving rating, the agency vehicles all get special abilities, too. The fast-moving supercar gets machine guns, the SUV gains the ability to jump, and the big rig gets a turbo boost that helps it get up to ramming speed. You also have an explosion rating. As you blow up enemies with grenades or rockets, you gain points in this statistic. Leveling it up increases the radius of your explosive weapons, which is silly when you stop and think about it but devastating and exciting at the same time. So you'll start out at the beginning as a fairly weak cop, but by the end, your increased abilities make the game feel nicely different. Using those abilities and exploring the large city is what makes Crackdown fun.

When you get into agency vehicles, they'll transform a bit depending on your driving skill.

While you can certainly go through Crackdown by yourself, and it won't take too much time to eliminate all the bosses, you can also play cooperatively. The game tries to make the co-op a seamless experience, but in reality, it's anything but. When you're playing alone, you can set an option to allow other players to request to join your game. You can limit this to friends, if you like, but either way, you can always deny a request if you're in the middle of something. If you accept, the player doesn't jump in alongside you or anything. Instead, you're kicked out of the game, and you have to reload to get back in. If that other player quits, your game ends, as well. A more on-the-fly join/quit setup would have made this mode a bit more effective. Also, the joining player joins the host's version of the city. So if you've beaten the game, joining players aren't going to have much to do, unless you want to set up some impromptu racing contests or devise your own rules for some kind of "who can throw this car on top of this building" competition. New players playing co-op with experienced vets won't get much out of the experience, either, because the easy boss battles become even easier when you're jacked up--the first few just require you to get onto a roof and gun down the boss, which is simple when your jumping is maxed out, but those newer players will have to take the stairs, and by the time they get up there, the fun is already done. So you'll want to find someone that's near the same spot you are in the game, if you want to enjoy it.