Tower defence games are a thriving genera on the iPhone with many, many games, some good, some great and some just plain bad. Today were going to be taking a look at one of the better TD games, Star Defence from ngmoco.

Star Defence follows the usual tower defence premise: bad guys, aliens in this case, invade and it’s your job to stop them dead in their tracks. The stand out feature for Star Defence has to be it’s 3D rotating worlds that you fight on. Instead of a field arena, you get small planets on which the path of the enemy is fixed. This takes some getting used to at first, especially if you’re used to the classic kind of playing field provided by the excellent Fieldrunners, but it’s well worth the effort. The graphics provided in Star Defence are really quite good and look akin to the graphics provided by Command and Conquer Generals, allowing you to zoom right in on the action for close ups with the units which are all pretty well animated.

With that kind of 3D graphics you might expect the performance of the game to be bogged down, but even on a 3G, the game handles perfectly. Even when you get a boat load of enemies trashing through your towers the action is smooth and rapid. It’s a testament both to the iPhone’s prowess but also to the programming skill put in on the game. In fact is clear that ngmoco have put some effort into optimising the experience on the iPhone as all the controls are intuitive and a perfect fit for the touch screen device.

As game play goes Star Defence has a solid 8 levels of play with a good variety of enemy and towers to vanquish them with. You’ve got Gatling lasers, Fire guns, Slow guns, Tesla towers and my personal favourite, the Rail gun, to make sure those pesky critters don’t get to your base.

Star Defence also packs a decent online element being able to send challenges to friends through Plus+, a free online scoreboard and multiplayer service. It also includes achievements, which can be obtained similar to those on the Xbox 360 or PS3. It adds a an edge of competitiveness to the game, giving you something more than simply finishing the game to aim for. Each achievement also adds to your Plus+ points giving you a overall rank which can be added to via any Plus+ enabled game. Twitter and Facebook connect has also been recently implemented so you can annoy your friends every time you beat a level (is it just me that finds that deeply irritating?).

Overall, Star Defence combines great graphics with decent game play and longevity added to via achievements and online challenges. If you’re a fan of tower defence games then this is a must buy. For everyone else Star Defence is highly recommended and the least you should do is check out the free Star Defence Prelude for a taster if you’re still not sure. I for one love this game so much (and I actually paid for this one), I really hope that they make a sequel.

Star Defence is currently available in the App Store for the bargain price of 99c (£0.59) with a free ‘trial’ version called Star Defence Prelude, which chronicles the first battle with the S’rath over Outpost D-13.