When it comes to iPhone/iPod games, publisher ngmoco has become a forced to be reckoned with. Past titles such as Rolando, Word Fu, Topple and Dropship have captured the imagination of many, so you can be sure that when they release a new game fans will flock to it. Now with developer Roughcookie, ngmoco takes full advantage of the new iPhone OS 3.0 and gives us a tower defense game for the iPhone like no other.

The basics of Star Defense are no different from any other tower defender, destroy your enemies before they destroy you. You need to defend your base from enemies, who are deployed from an insertion point. As they progress along a maze like path, you place towers along the way to defend your shield wall from hordes of S’rath invaders. You earn credits for each kill, which in turn allows you to buy more towers or upgrade your existing ones, survive for a certain number of waves, and win.

The five tower types are as follows; Neo-Plasma Blasters, which have a damage over time effect; DX-3 Cannons, which slow enemies; the Gauss Turrets, your standard low-cost tower; Phase Coils, which do area effect damage, and the Quantum Launchers do high single target damage. Each can be upgraded, for a fee, or scraped with the ability to earn some cash for scraping it. Each tower has a damage type which effects different enemies in different ways. Some of the S’rath are resistant to fire, so your Neo-Plasma Blasters are ineffective, while others can easily be brought down with one shot of the Quantum Launchers. This forces you to have a variety of towers, deciding which can be most effective against the hordes attacking you.

What really sets Star Defense apart from the other tower defense games is the presentation. You’re building towers on 3D spheres and cubes, constantly managing the viewport using standard iPhone gestures. Pinch in and out to zoom in and out, a single finger swipe moves the camera, and two fingers on the screen rotates it. When buying a tower simply drag it to where you want it. To upgrade double tap a tower to get the upgrade/sell option. To speed up the game in the early stages you can choose to usher in the next wave prematurely with a simple tap. While it might seem insignificant, it adds to the strategy of the game. If you have large enemies that you don’t have the firepower to stop simply send in a weaker wave, kill them and get the credits to buy a tower to stop the large one.

Star Defense offers three levels of difficulty, Easy, Normal and Hard. Playing the game on Easy is well, easy. Normal can be a bit of a challenge, but Hard is absolutely brutal. To make things even more interesting ngmoco has added a Challenge mode. A great feature that allows you to submit your score to Twitter and Facebook, and challenge friends. It highlights just one aspect of how ngmoco is really trying to expand what an iPhone game is. They’ve added achievements, or commendations, to add a sense of a console feel to it. You can register your account so your scores and commendation list can be shared with friends, further adding a competitive spirit to the game.

It’s also been revealed that you’ll be able to add another galaxy to the game via micro transactions, in the form of DLC add-on packs. This allows for the game to expand and present new challenges as well as offer a larger variety of levels. The best part is that with the use of the OS 3.0, all transactions will performed in game, making it a seamless experience.

If you’re into tower defense games the Star Defense is an absolute must have. The presentation, gameplay and challenge features make this one of the best iPhone games out there. For $5.99 you really can’t go wrong.