Made in the spirit of X-Com, but definitely a different game. Real time tactics combined with empirebuilding-like play.
Certainly the game feels much like X-Com, with a sense of unknown and a focus on researching new tools and squad-based combat. A fairly decent tutorial is given to begin with, but after that the start of the game can be difficult. With no means of manufacture and no weapons researched, your squad members are both rookies and dependent on captured alien weapons.
Fortunately this changes quickly, as you capture a base very swiftly. The base construction is a little simplistic and clunky, but easy to master, and soon enough you can crank out some research into your basic projectile weapons, and start harvesting your resources.
Resources are harvested by province, with many provinces yielding bases instead. Bases can't be worked on unless connected by tracks for supplies, and neither can far off resources be gathered without track connections. This track is very expensive to maintain, so learning the most efficient way to connect territories is an important skill. Resource distribution is very random though, so you may spend much of the game hunting out a province for the one you're in short supply.
There's an alternative, however. If you have a surplus, you can simply give it to one of the three factions -- Human, Cyborg, Psychic -- to up your relations with them. Or, if you have good relations, you can request supplies from them. This resets your relations, so be sure to request and then, if you want good relations, give them your extra or go on a mission for them. Good relations also allows you to hire stronger soldiers of that type.
Soldier advancement is much cleaner than in some games, and is a hybrid of skill and level-based advancement. Every few missions, a soldier will level up, and can improve one of their basic stats. Their other abilities such as shooting, speed, carrying capacity, and the like are all derived from these stats, and go up as the player assigns points. To add a further twist, qualified soldiers can be trained in MOS-type areas, gaining the ability to use advanced equipment such as high-tech medkits or sniper rifles, or special abilities such as targeting hit locations or using two weapons at once.
The actual combat is done at squad level, and is NOT turn-based. Instead, it's a simultaneous action-based system where you give the soldiers orders, and can pause at any time to issue or cancel orders. One of the annoyances in this system is the soldiers and their whiny voice acting, but this can be disabled easily enough. As this is the meat of the game, I do have to say... it's very fun, but has some downfalls. The maps aren't exactly randomly generated, leading to a limited number of terrains that are quickly memorized. Unlike X-Com, your soldiers can actually take a hit or two without dying, so you can be a little more daring. At first, the enemy selection is pitiful and not varied much, between aliens and mutants. Pre-scripted events occur at certain times in the game that are both more difficult, and offer surprises and new enemies and technologies.
I have to say it though... the time scale on this game is screwed up. You'll do major advances and battles within hours or days. While it's not too bad, since everything is on that same scale, it does make it a little hard to believe at times, ruining some of the immersion. Also, the best weapons technology is undoubtedly the regular old assault rifle, which is bizarre. Lasers are only useful for capturing, since they do a lot of stun. Several people have made weapon rebalancing mods to make things more interesting for the advanced tech, and I recommend using one of those. The game is fun without, but I think it feels better with powerful weapons becoming available. Besides the funfun underbarrel grenade launcher.
One criticism this game has gotten is a lack of stability and bugs. Bugs maybe, I've seen some odd behavior, but stability hasn't been an issue for me. I believe many of the problems can be traced to the Starforce copy protection included in the game, as I've heard some people have conflicts with it. I'd recommend patching and removing Starforce before ever running the game, if possible.
Finally, the graphics are sub-par for the hardware requirements. Sorry, but it's true. They're still good enough, but a little brighter textures and smoother rendering in places would have been nice.
I won't lie and say this approaches X-Com in quality, but for those of us wanting a newer, similar experience who don't mind some differences, Aftershock is one of the best games to come around in a while. If not for some of the quirky behavior and design flaws, this would have scored much higher. As it is, if you can pick it up for $30 or so, and have the time, it's a worthy investment.