Aaaanyway, Stalker. The three games under this title (Shadow of Chernobyl, Clear Sky, and Call of Pripyat) all take place in the mysterious realm called the Zone, created with the nuclear reactor at Chernobyl went even more berserk than it did in real life. The Zone is now host to mutant animals, strange anomalies that warp space, artifacts with strange and mysterious properties, and hordes of armed men of various factions wandering about. Some, the Stalkers, gather artifacts for cash. Others are in factions warring for power, such as Duty, Freedom, and the Monolith. The three games offer similar storylines, where you are sent into the Zone to solve a mystery or find some fabled goal.
It sounds like a typical computer game, but it's not. The game is all about mood. The Zone is a desolate place, all right, and if you've ever seen photos of the rotting towns around Chernobyl you'll understand that it's a particularly compelling desolation. The developers added a weather system, and a scheme called A-life to give the wildlife and NPCs some activity; as you play, you might see creatures in the distancen attacking each other, or two rival factions shooting up the landscape. Add in some fascinating sound design, and the Zone feels like a real place.
(The games have an odd relationship to the outside world. Their origin lies in _Roadside Picnic_, the magnificent SF novel by the Strugatski Brothers written in the mid 1970s. That novel was adapted, very freely, by Soviet filmmaker Andrei Tarkovsky as _Stalker_. Years later, after the Chernobyl disaster, many people noted similarities between the exclusion zone and the movie, thus making both book and movie seem prophetic. So GSC Gameworld, a Ukrainian company, had a lot of material to boil into a game. And thanks to the game, people actually dress up in Stalker gear and play at being "in the game"-- in the actual Exclusion Zone of the Ukraine. It's sort of a national myth in the same way that _Blade Runner_ is Los Angeles's official nightmare.)
The games are far from perfect. The stories are _really muddled_, and the original releases were pretty buggy. Accounts have it that the game was originally far more ambitious, with alrger areas to explore, a more complicated storyline, and better A-life, but the developers stripped it down to something they could get out the door close to deadline. And while GSC Gameworld went belly-up, and many of its people are working on a forthcoming Stalkerish multiplayer game called _Survarium_, fans have been developing mods which fix the games's copious bugs and upgrade the graphics, such as Stalker Complete.
Stalker: Lost Alpha is an odd mod, because it attempts to upgrade Stalker to its original scope. The maps are bigger. There are more characters, more monsters, more places to explore. They've managed to incorporate drivable vehicles. The modders went through old screenshots, legacy code, and the like to recreate all of the stuff that the original gamemakers intended. It's finally in a form that can be played reasonably well, and one can download and play it as a standalone game. If you want to try it, it's at http://www.moddb.com/mods/lost-alpha.
I'm not very far into the game, but here's my review: it's only okay. It has a LOT more to play with, but somehow, it doesn't have that wonderful, fatalistic desolation of the Zone we got in the first game. There's a lot longer travel between the trouble spots. For example, when you reach the Bar in the actual release version, it's a brief trot through a rusty factory before you're there. But in this new/older version, you have to walk all the way around the factory before maybe finding the entrance, adding an unnecessary five minutes to the game. There's less dialogue and character, but that's understandable, because the modders aren't a full studio.
But, if you're not playing anything at the moment, and want to acquire a large and compelling game for free, check it out.