Remember Xenonauts, a.k.a. Cold-War-meets-XCOM? This turn-based single player strategy let you defend Earth from an alien invasion with what resources human nations had in the middle of the 20th century. As you probably know, Xenonauts 2 is on the way basically it is a prettier and better version of the original game and now it has a free playable demo available on GOG.com. This early pre-alpha build features a skirmish, in which a squad of soldiers takes on some aliens somewhere on the surface of our planet.
Note that the demo is available only temporarily and will be removed from your GOG Galaxy account when the paid phase of Early Access starts on GOG and Steam. If you prefer to have a quick look at the game instead of playing it yourself, there is a gameplay video from the demo posted on YouTube by Yeti.
The first difference you will probable notice between the first Xenonauts and its sequel is that Xenonauts 2 is in 3D, as it is powered by Unity Engine. It also has simulation of physics, improved management and tactics as well as a score of other enhancements, but in terms of gameplay its still very similar to what the fans already know.