a true classic...
You start off as a commander of one base, funded by worldwide funds from different states, whose goal is to battle the oncoming alien invasion. Nothing serious at first, just a few small scout UFOs, only after some time your management grows to several bases, larger UFOs and terrorist alien attacks on towns. This global base management, building of structures, buying of weapons, chasing down UFOs and scouting the map, is the first part, the strategical, part of the gameplay. While this part is not bad, it is not overly brilliant either.
The real fun begins once you shoot down an UFO or land in a terorized city. The strategical view switches to an isometric turn-based combat where you get to control the squad you sent there and eliminate the aliens. The aliens come in some varieties, which have different abilities and different weaknesses. To battle them you can use standard guns, research better weapons, or even research alien technology to gain the the best weapons and armor in your fight against the alien invasion. You can even research aliens themselves, either alive or dead, to find out their weaknesses.
Sounds simple? Well, it basicly is, but that doesn't mean it can't be louds of fun. What makes really this gem so spectacular and enthralling is the atmosphere which even today, after all these years, feels unique and dreadful. A great part of this atmosphere is the dreadful setting, in a town where every turn civilians die, or even just at some farmstead where you can see the crashed UFO partly of fire. Another great part of the atmosphere is the sound. The sound and music score is, in my humble opinion, perfect. Sure it is no symfonic orchestra considering it was made way back 1993, but still, it is enchanting and horrifying at the same time.
It is truly difficult to explain why this game is so good. My best bet is the perfect atmosphere in the missions, the simply yet finely tuned strategical element and the, at first strange, but later realized to be well balanced, combination of strategy and turn-based action. Truly a masterpiece.