Its easy to become emotionally invested in the constant tug-of-war with the alien invaders.

X-COM: UFO Defense has come to define our memories of the series.

When designer Julian Gollop began work with his brother Nick on a sequel to 1988's Laser Squad -- a sequel that would eventually become X-COM: UFO Defense -- I wonder if he knew what he was getting into.By the early 1990s, Gollop had been developing games for some 10 years, all of them turn-based tactics or conquest games of one sort or another. His very first game -- Time Lords -- was a large-scale galactic conquest game, while Laser Squad and Rebelstar laid down a foundation of tactical ground combat. It was Microprose that ultimately pushed Gollop to find a way to create a fusion of these two systems and create the game that we know today as X-COM.Playing it again in 2012, it comes off as both completely brilliant and slightly insane. In effect, X-COM melds an SSI Gold Box RPG with a highly detailed 4X game like Masters of Orion, making it in some ways two entirely different games. It might seem to be par for the course for the genre, but most games -- even more ambitious ones -- will often choose to focus on one side of the coin while keeping the other relatively simple. X-COM, by contrast, manages to make both its tactical ground combat and its overarching "Geoscape" global management feel like separate and fully developed games, which continues to be its greatest strength even today. Mainly because there isn't much like it.Of course, its greatest strength is also what can make it seem near-impenetrable for new players. Even placing the first base can seem daunting, as there are no set hard points on the map. Unless you take the time to consult the manual -- not a common practice in an age of built-in tutorials -- the advantages of placing the base in Europe vs. North America are unclear. Morever, patience is required to navigate a somewhat archaic interface that conveys much of its info through murky statistics and graphics, and that can be in short supply when aliens are conducting terror raids on major cities.But it's in the chunky, polygonal map and the reams of numbers where a kind of story arc begins to emerge. It's in our nature to lend meaning to seemingly random events, and in that its easy to become emotionally invested in the constant tug-of-war with the alien invaders, the lives (and, more often than not, the deaths) of virtual troopers, and the all-consuming battle for money. Even the standard Let's Play can't help but take the form of a narrative, as in the case of this elaborate recount of a particular game. It's from there that X-COM is elevated from statistics and map markers, and into the realm of memory.X-COM works because of the almost obscene level of detail the Gollops invested in the mechanics, as well as because of the aliens themselves. The soldiers are not robots -- they will turn and flee if their morale drops low enough, or even go berserk and turn on their teammates. Ammunition isn't free either; in fact, it tends to be in critically short supply through most of the game. It's even possible to forget to load it up for missions, which everyone who has ever played X-COM has done at some point.The aliens, of course, have their own motives. It's never entirely clear what they're going for at any given moment, which is by design. An element of randomness is actually built into their AI, which can occasionally make them seem smarter than they actually are, as well as make them all the more unpredictable. On top of that, they will actively seek to destroy your bases, conduct terror raids on civilian cities, and even cut deals to take your funding countries out of the war.This intricate dance has rarely been replicated. Partly because of the niche nature of the genre, and because of the surplus of moving parts. Even veteran developers can end up crashing and burning when they stretch themselves too far, which is exactly what happened with Stardock and the ill-fated Elemental: War of Magic. It's just not that easy to develop a game of X-COM's ambition and scope.Conversely, it's easy for even hardened PC gamers to feel shy about investing in a challenge as unforgiving as X-COM. Failure is frequent and the body count is quite high, which is a common feature of old-school PC strategy games. The reward is in the story that slowly but surely develops as troops mature, bases are built, and alien technology is reverse engineered into workable equipment. When it comes time to take the fight to the enemy stronghold, it feels like the end of an epic.X-COM: UFO Defense felt like lightning in a bottle, and as I'll discuss in the second part of this retrospective, it turned out to be difficult to replicate. But the original definitely touched a nerve, whether because of its novelty, mechanics, or its difficulty which has made it possible for X-COM to maintain a large following to this day, 17 years later. It's because of the personal touches it lends to one of the most impersonal genres in gaming, whether in allowing you to name your troopers or design your bases. It's those features that make me feel as if I'm playing something larger than myself.As such, it's not surprising that X-COM: UFO Defense has come to define our memories of the series. Firaxis certainly seems to think so, as evidenced by the fact that they're calling their revival X-COM: Enemy Unknown -- a combination of the original European name, UFO: Enemy Unknown, and the American X-COM: UFO Defense. If you're going to start from zero, then UFO Defense is where you begin.Of course, given the phenomenal success of the original game, Microprose was hardly willing to let it rest without a sequel or two. The real question is whether those sequels were doomed to failure from the start, or there was legitimate room for the series to grow. Drop by on Thursday as I do my best to answer this question, and others, as GameSpy's week-long X-COM retrospective continues.