I was going to post a mini-review I wrote in a seperate post.. then I noticed this thread so I'll post it here:
My current favorite game is Robo Defense, and at this point it is the best game I've played on the system (with the possible exception of the NESoid... because that allows you to play 100's of NES games.. which is kind of a special thing). Robo Defense is essentially a Tower Defense style game... but it is an extremely well executed version of the genre. If somebody reads this who hasn't played a Tower Defense game.. the basic idea is that bad guys come out from one side of the screen and try to get to the other side of the screen. All you really do is build towers to shoot/zap/explode the bad guys before they get to the other side. The depth (and fun) of the game comes from the idea that some 'bad guys' have weaknesses to certain towers while others have a strong resistence to the same tower. So you have to be careful which towers to build where and how many to build (because you have a budget of cash which goes up as you kill stuff). That's the basic idea... and there are 100's of these types of games out there for almost every system.
This game is surprsingly deep, but it is extremely easy to play. What this game does so well is that you only start out with three options for building stuff (gun tower, rocket tower and slow down tower).. and you literally drag the towers from the bottom of the screen to the spot where you want them to go (which is faster and easier than other games I've played). Other tower games I've played are too intimidating because they have like 20 towers which do different things.. it's hard to get started. Here you just have three.. then you upgrade the hell out of them as you go. It feels more intuitive and simple. Once you start upgrading you can make a lot weapons... anti-air guns, land to air missiles, mortars, artillery etc. The graphics are really nice and the game runs nice and smooth. Plus the game even has achievements (which is a first for me in a phone game). And you can spend points you earn to buy upgrades (like more powerful bullets and rockets etc).
It's a top notch game. Great design, polished look and interface. And most importantly.. lots of fun.