A game by Chromite Software. It is Mac based and therefore I have not yet played it. The little bit of information below is directly from Chromite Software's Website.

Galactic Core is a game of exploration, strategy and carnage in the depths of space.

You play one of six unique species locked in lethal warfare. Hop from planet to planet, colonizing the new worlds, creating new fleets, and attempting to overwhelm the enemy. Decide what to research, exploit the resources of your worlds, and decide what to build. Choose between huge warships and unusual strategic vessels, like planet killers and holographic vessels.

Galactic Core comes with six campaigns, designed to provide many hours of challenge and torment. When you have completed them, however, the game is far from done. Use the campaign editor to make your own scenarios, and download new ones off the net. You can have Galactic Core create a random map.

You can even take the battle to your friends! Galactic Core features play by E-mail. Meet new opponents on the Spiderweb Software message boards and fight them from afar.

Galactic Core is a complex and exciting game of exploration and conquest, designed to be accessible to the novice player. Don't worry about wading through unending rules. Just get out there and seize the galaxy!