Sid Meier's Alien Crossfire demo

It is a time of upheaval on Planet. The original inhabitants of Alpha Centauri have returned to reclaim their world.

The aliens, though, are split in a brutal struggle. They engage in battle over Planet, nearly destroying each other in the process. The survivors jettison to Planet's surface where humanity has been building a new home. Now the humans from Earth are caught in the crossfire. Will they band together to defeat the aliens or will other alliances be formed?
Sid Meier's Alien Crossfire, the official expansion pack to the critically acclaimed Sid Meier's Alpha Centauri, features seven new playable factions, several new technologies and secret projects, and a new plot that continues the story of humanity's struggle to colonize a hostile alien world.