Dyson is a free cross-platform real time strategy game with abstract visuals. It manages to be simple and elegant even as it combines elements such as the emergence of life, a Darwinian "sperm wars" motif, and intra-species competition with your standard world-domination game concept.
This is an award title that has been nominated as a finalist at the 11th Annual Independent Game Festival. Dyson is really a wargame, and a terrific one at that. You start off with a single "seed" placed on a lone asteroid, which blooms into a sort of tree that generates more seeds (initially I was going to title this posting "Dyson: spread your seed across the universe" but decided against it ). Your objective: to colonize the entire section of the universe/asteroid belt that you inhabit, driving off your competition.
http://rapidshare.com/files/196448304/Dyson108.kostrzewski.rar