1. Apologize and give 100 pounds tribute to Celts
2. Promise to make amends, but do nothing.
3. Send Celtic messenger's head back on a platter."

Basically, start on a planet ideal for you. Build ships to explore+colonize nearby worlds. Terraform to make the planets habitable + mine to get metal to build more ships. Research six different areas of technology to get faster, longer range, more powerful ships which take less metal to build. A variety of human and computer opponents are trying to do the same thing. (Although their idea of an ideal planet is different from yours.) Size and shape of galaxy are customizable. Computer opponents get advantages to make up for AI, although I find the AI to be pretty good overall. The Mac version networks in seconds: don't know how good the PC will be.

There's a lot of humor in the game: sending a ship to a planet causes the computer to say "YAHH!", many other sound effects are similar. The ships you design during the game play often have very funny pictures. (My favorite looks like a skull+ribcage with a V-8 motor in the back.)

I'm not sure how the Windows version compares rulewise: The Mac version just underwent a major upgrade to add alliances, improved shipbuilding finances, better messaging between players, etc.

Overall, I love it. Be forewarned: getting this game while still interested in Civ may end in ruined career, marriage, etc...

Haven't played it, but looks like you can control the production/distribution of resources into a space program.

Very similar to Castles, but has cities which you can control production in (build city walls, expand city, improve health, train army, etc). You use your cities to build an army, then direct it to go to an enemy city and besiege it until it surrenders. Your armies can fight the enemies' armies on battle fields in real time and in 3D overview. If you prefer the combat in Civilization and don't like spending the time constructing stuff, making trade routes, getting advances, etc, then you might like this game.