So, nobody likes paid apps. Really, why should you pay for this stuff?<P> Meanwhile, some apps (especially gaming) tend to want money for what they do. Robo defense is one of such apps. It's a delightful tower defense game worth playing again and again. It can be as hard as you want it to be, although plenty of the achievements cannot be accomplished without a ton of upgrades. For the tower defense fans, it tends to lean towards this type or the spiral defense type stuff. If you prefer the latter, there are plenty of separate apps for that. All in all, this is worth it, with it's creative missiles/guns/etc.