The tower defense genre is broken, and CastleStorm is here to fix it.

Tower defense means something a little different to everyone, but the gist is this: protect yourself from an onslaught of enemy troops using artillery towers that you don't control directly. There are plenty of variants on this theme, but that offense vs. defense matchup is the core element that remains unchanged. While there's still plenty to be enjoyed in this genre, the lack of any real innovation has led to a glut of lackluster "me too" efforts. Zen Studios' CastleStorm flips the traditional formula on its head, giving you all the same weapons and tools your opponents have. You'll fire a powerful ballistae, command troops, cast spells, and take control of heroes with the ultimate goal of destroying your opponent's castle or stealing their flag before they use their arsenal to do the same against you.

The offensive approach isn't the only thing that makes the game special, though. While many games would settle for a single approach to combat, CastleStorm offers real variety in the tools available to achieve your goal. Although there are only two win conditions for each match, how to mount an offensive is completely up to you. Focusing attention on direct attacks to the enemy castle is just as valid as micromanaging ground troops and hero units. Most players will likely adopt a more well-rounded strategy, which means you'll constantly be switching back and forth between different battlefield tactics. This makes for exciting, fast-paced strategic gameplay where you often don't get a second of down time.

Despite the sheer number of actions you can perform in every mission, its quick and easy to switch between functions. That's a good thing, too, because you'll often find yourself in a sticky situation where you'll need to defend against an enemy onslaught at a moment's notice. The PC version of the game offers keyboard and controller support, but the game was clearly designed with the Xbox 360 controller in mind. I found that to be the best way to play the game. Aiming your ballista can be finicky at first using this method while the mouse and keyboard controls offer pinpoint accuracy (if that's what matters most to you).

In addition to the different tactical choices offered during missions, there are plenty of opportunities between assaults to upgrade your castle, troops, and equipment. You'll begin with a few basic tools but before long you'll have a few dozen choices to make before each battle starts. If you're very particular, you can even build a completely custom castle from scratch, though I found the default options more than adequate for the campaign. The gold you earn from each mission can be used to upgrade everything from your ballista ammo to rooms in your castle, but it's often hard to tell what kind of real impact your upgrades are making. It would have been nice to see more fun and unique upgrades instead of what amounts to numbers on a spreadsheet.

All this variety is nice, but it overreaches at times. The game offers occasional side missions that aren't nearly as compelling as castle versus castle combat, but the gold rewards of these diversions are too lucrative to pass up. In addition, the different types of missions put the difficulty curve all over the map. You'll easily crush the opponent in some and find yourself retrying others over and over again to find their one weak spot. Two missions in particular have precise paths to victory that are not immediately obvious. In a game that rewards careful strategy and time management, this kind of trial-and-error feels out of place.

Fortunately, CastleStorm's multiplayer doesn't suffer from any of those missteps. The headlining modes on display here are pure castle versus castle devastation, putting two players head-to-head in either split-screen or online play. The intersection of action and strategy are perfect against a buddy, and the tide of battle can change constantly. If head-to-head combat isn't your thing, there's also co-op where one player controls the ballista and the other handles ground forces against endless waves of enemies.

CastleStorm is a welcome evolution of a genre that has quickly become stale. Its multiple layers of gameplay fit together well and provide a surprisingly deep experience that always keeps you engaged in the action. It's a game that truly transcends existing gameplay paradigms and brings something completely new to the table. At its core, CastleStorm is a game about variety, and every mode and mission offered in this robust package is executed with style and precision.