Developers of the free game UFO: Alien Invasion
have released a new version of this turn-based tactical combat strategy game inspired by the X-Com series and powered by a heavily modified version of the Quake 2 engine. UFO Alien Invasion offers tactical combat against hostile alien forces which are about to infiltrate earth at this very moment. You are in command of a small special unit which has been founded to face the alien strike force. To be successful on the long run, you will also have to have a research team study the aliens and their technologies in order to learn as much as possible about their technology, their goals and the aliens themselves.
Visit the official website
for more details.