The listing, Planetary Annihilation [SteamKey] has ended.
Colonize solar systems, annihilate homeworlds, and exterminate your foes in epic interplanetary battles with multiple players and thousands of units. Planetary Annihilation takes strategy gaming to a never-before-seen scale -- and gives players powerful tools to control the action.
Blow up everything, anywhere; dominate with punishing spacecraft, robots, and other futuristic machines of war. Arm asteroids and send them on planet-destroying collision courses. And take over an entire galaxy in a dynamic single-player mode with procedurally generated content. Don’t just win, annihilate!
http://store.steampowered.com/app/233250/