You need the Gphone to play Spira Defense by Craig Hart.

I just downloaded it from the Android Market today while sitting in a coffee shop in Los Gatos and was pleasantly surprised. The tiny controls for the game are a little tough to click on with my fat-ish fingers but other than that the game plays like a first rate tower defense. It feels very much like a streamline combination of Vector TD and Circle TD.

There are only 3 towers in Spira; Rapid (fast rate, long range), Chain (high damage, multi targeting) and Slower (Slows enemies, multi targeting). After building each tower you are given the option to upgrade the damage, range and special of each tower. This is a feature I believe should be common to most tower defense games but seems to be quite rare.

I haven’t had time to figure out what all the special abilities are for. I plan to write an article later going into specials and discussing some basic strategy.