Although there's not really much to do other than playing the game over and over again trying to beat your highscores, it's hard to criticize Army Defender. It does a good job of bringing the popular "defense" game to DSiWare and is fun to play. With its 200 DSi Points price tag it's also extremely cheap, making it one of the better choices in said price range.
Video games can do what few other mediums can: awaken a sense of pride among casual observers. Everyone feels better after slaughtering a few thousand baddies or saving the world from yet another space invasion -- it feels like a personal triumph to see one's on-screen representation accomplish something, anything. For all that few in the DSiWare community will end up defending a fort from infinite hordes of heavily weaponed enemies, they do it in Army Defender, and it feels satisfying in the way that only video games can.
Pocket Gamer:
By definition, a castle defence game is static.
That's why castles went out of fashion. By the time gunpowder had been invented, anything that didn't move was going to get blasted by large numbers of lead balls.
To that extent then, as with so many game genres, with castle defence you're managing the process of inevitable defeat. As you get better defences, so the attacking waves become larger and more powerful. Eventually you're overwhelmed.
This is the case with Army Defender, which quickly ramps up the number of enemies you have to deal with, although it doesn't compensate you in terms of new super weapons. You start off with a good selection, however.
