Robo Defense is a tower defense game for Google Android. Basically your job is to prevent enemy vehicles from getting from one side of the board to the other. But while the enemy troops can drive, run, or fly, all you’ve got to work with are stationary guns, rocket launchers, anti-aircraft missile launchers, and “slow towers,” which slow down enemy units.
After demolishing a few enemy units, you’ll have enough credit to either buy more units of your own or to upgrade your units to give them a little more punch or to convert them from, say, a gun, to an anti-air cannon.

There’s a free version of Robo Defense available for download from the Android Market, and you could easily spend hours playing it at different levels of difficulty. But if you want to unlock additional game maps, you’ll want to shell out $2.99 for the full version. Robo Defense is the first Android app I paid for, after realizing just how addicted I’d become to the free version.
There are 4 maps in the full version, plus “VR Training” mode, which allows you to customize the map or play on a random map. There are also 20 levels of difficulty, which makes the game more challenging as you move along. And you gain points during each game which you can spend on upgrading the capabilities of your units in between games.
Robo Defense also challenges you to reach a number of different “achievements” such as completing a map without any slow towers, or reaching a score over over a million or 50 million lifetime points. You can spend a lot of time playing Robo Defense without reaching half of the achievements.
You can check out more photos of the game after the break.