Phage Wars is an excellent Real Time Strategy Flash game. You pick a type of ‘phage’ (which is technically a kind of virus that infects bacteria), and your aim is to conquor territory (cells). Each cell will then make more of your phage, and you can infect other cells. Bigger cells make phage faster.
You have competition, in the form of other forms of phage. If the competing phages wipe our your phage, you’re extinct, and you’ll have to try that level again.
It’s good easy fun, and not quite as hard as Nano War, which is a very similar game. The graphics in Phage Wars are superior, as is the sound, but the difficulty isn’t quite high enough to provide the necessary level of addiction.