Siege of Centauri

Siege of Centauri puts you in command of the defense of Earth's first interstellar colony. Thousands of alien machines are descending on the helpless colony and only you, with your arsenal of fast-deployed orbital defense structures (FODS) can stop them.

The enemy comes in all shapes and sizes, challenging you to counter them with the right defense in the right place. Siege of Centauri combines the best elements of classic tower defense games with the strategic depth Stardock has delivered in past titles, including Sins of a Solar Empire: Rebellion and Ashes of the Singularity.

Battle across the surface of an alien world through a series of story-driven campaigns or fight for survival in a doomed region to see how your skills match up against thousands of other players across the world.

Source: Steam Store Description