Xenonauts

Xenonauts is a strategy game in which you control a multi-national military organisation defending a Cold War-era Earth from alien invasion, using small squads of persistent soldiers to eliminate the extraterrestrials and recover their technology in turn-based ground combat.

A detailed strategic layer allows you to co-ordinate the defence of the planet, using your interceptors to shoot down UFOs and researching captured artefacts to learn about your foes and unlock new combat equipment to use on your missions.