There is by no means any kind of shortage of tower defense games for the iPhone, and for a good reason. The genre works great with the touch screen controls, and most of the games are fantastic for playing for a few minutes at a time on the go. We've recently got word of two new contenders throwing their hat in to the tower defense ring:
Bloons Tower Defense - Playing on the success of the balloon popping game Bloons [99¢ / Free], Digital Goldfish recently released this trailer for their tower defense spinoff game. Similar to Bloons, Bloons Tower Defense also started as a popular flash game. Will Bloons Tower Defense see the same positioning on the App Store top ten as Bloons did? It's hard to say, but if they can recruit the army of Bloons players in to being tower defense junkies, they will really be on to something.
Moonlight Minions - Another 2D tower defense game with a few unique twists and a very nice art style. Each monster in game has their own abilities such as being able to teleport, spawn hatchlings, or even go in to stealth mode. To cope with these abilities, in addition to the array of towers there's also a bar along the bottom with three different powers you can use. The lightning bolt does heavy damage to a single target and stuns nearby monsters, the earthquake briefly stuns all the monsters when you shake the iPhone, and there's even a meteor shower that does periodic area effect damage. Also included are two different boss types which also have their own powers too.
Both Bloons Tower Defense and Moonlight Minions are coming soon.