For those who don't know what XCOM is, please read the whole OP. It will tell you all about original XCOM. At this point, there are so many gameplay videos and reviews out there that it would be an unnecessary duplication of effort to describe it all. This review is for people who played the original XCOM, and are wondering whether to buy the new one.
The answer: Buy it. But have realistic expectations. It's not going to be a 100% remake of XCOM, it's more like the low-fat version. Tastes very similar, but doesn't quite have the same rich creamy goodness as the original. But if you haven't had ice cream in ten years, are you really going to complain if someone gives you low-fat frozen yogurt?
Now let's talk gameplay mechanics:
No TU system: The new system is adequate, but it's like drawing with crayons compared with the watercolor finesse of the TU system. You can shoot, move-and-shoot, or move-and-reaction fire (now called overwatch). Some units (heavy weapons, snipers) can only move, shoot or overwatch. There are abilities that you unlock with each soldier's XP to modify these mechanics, but that's basically it. Reloads burn your entire turn. Heavies can switch from machine gun to rockets instantaneously. Tactical gameplay is noticeably faster, but that's what happens when you're drawing with crayons. You'll miss it, but you'll get used to the new system. Just thank the gaming gods they didn't dumb-it-down more.
4-6 soldiers: Four soldiers sucks. But luckily, getting to six soldiers doesn't take long. Just try to get one guy to captain by letting him take all the kill shots. Six soldiers is almost okay. The reason is because unlike in original XCOM, units have full 360 line-of-sight awareness, rather than just a 90-degree pie-slice in-front of them. So, rather than needing three guys covering one flank, looking in all directions, you now only need one. Each soldier is stronger, with about 1.5x the firepower and 2-3x the health of an original soldier (just ballpark figures). Having only six soldiers does make losing soldiers devastating, so no more suicide rookies. You'll miss your big squads, but not as much as you think.
Cover system: The entire tactical game revolves around moving from cover to cover. I learned this the hard way. Original XCOM was all about overlapping arcs of fire, and setting up spotter-sniper shots. Cover was a secondary concern. Now it's the main show. It's not better-or-worse, but you will have to adapt to a new style.
Destructible environment: Impressively, they've managed to do this in true 3D environment. Most walls can be blown-open with weapons fire and explosives. But even so, the XCOM purist will notice a few things missing. Fire doesn't propagate, smoke doesn't choke. Objects do not have a blast resistance stat - they are either destructible or indestructible.
Soldier Inventory: Drastically simplified. There are now 4-5 unique slots. Primary weapon, pistol, armor, and one or two special items. Weapons are class-specific. It makes the game go much faster...now you're not dragging plasma rifles and plasma clips in the soldier loadout screen before each mission. On the whole, you won't miss it much very often, but you'll often wish you could switch out the pistol for something useful, like the stun rod/grenade (now called arc thrower). Some items are now folded into soldier abilities. Speaking of abilities, they actually work out pretty well, although I'm sure some abusive combos will be found soon. But for now, I'm actually enjoying them.
Base-management: Drastically simplified. If you're a micro-manager, you'll obviously hate it. You can't hire/fire engineers or scientists, they are now tied to a reward system. You don't have to worry about buying more missiles or ammo, they auto-replenish. Medpacks and other items aren't consumed after use in missions. Only one base, with an elaborate satellite/interceptor system to replace the other bases. Its a weak substitute, but it works, and it does save a lot of time. No need to worry about base logistics for your interceptor-radar bases anymore. It's a big time-saver, and it works well.
Day/Night: Unless there are some really subtle game mechanics I'm not aware of, the day/night difference has been completely removed. No more setting forests on fire and throwing out electro-flares. Personally, I avoided night-mssions anyways, so I don't really care.
Only one skyranger: It's a contrived choice, so that you must "choose" between saving two places, when any logical person would build up a force to big enough to respond in two places at once. It sucks, and it breaks the immersion of the game.
So, having basically criticized everything in the game, why should you still buy it? They've dumbed-it-down. Virtually every gameplay element has been compromised for console users. It's been simplified, made to play faster. There is a loss of realism. The original XCOM made you feel like a real commander fighting an alien invasion. Now you're forced to make arcade-game choices...do I want my soldier to get one free reaction shot, or gain a suppression ability? Should I save Australia or Japan? The original XCOM wouldn't have forced these artificial choices. The choices would have come organically from the balancing of priorities against limited resources, because the underlying game engine was sophisticated and realistic enough to create those hard decisions.
But you should still buy it, because despite it all, it's still got the soul of XCOM. The atmosphere, the unforgiving tactical game, the story line. By the way, the story narration is pretty fantastic. It's a genuinely fun game, and if you give it a chance, it will win your heart. To use one last analogy, if the original XCOM was Jurassic Park the novel, the new XCOM is Jurassic Park the movie. It's big, flashy, and stupid. But it's still fun.
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This remake looks legit, boys.
If you are too young to know what XCOM is, it is the greatest squad-based tactical game ever made. It was absolutely groundbreaking in its day. Fully-destructible environments, day-night lighting cycles, soldiers that panic and run, RPG-like stats for each soldier. And that's just half of the game.
In the original XCOM: UFO Defense, you start with a few million dollars from a council of nations to defend Earth from an alien invasion. You have just enough to build one modest base with spotty radar coverage. The alien UFOs easily outrun your troop transports, and they laugh at your fighter interceptors armed with cannons and missiles. The aliens whizz around the world, mere ghostly blips on your radars, as they infiltrate governments, and turn their politicians against you, and your funding begins to drop. They harvest humans and terrorize cities at will, leaving you to chase after them.
And so you do, with a Skyranger troop transport filled with fresh rookies, armed with rifles, autocannons, grenades, and rocket launchers. The aliens have plasma weapons and better night vision. You can kill the little gray men easily enough, but their robotic friends are insanely difficult to kill. You will easily level entire buildings trying to bring them down. Your soldiers can't shoot straight, missing easy shots before getting killed. When an officer dies, they panic and run wildly, or go into a catatonic state and refuse orders. In the worst case, they snap and start shooting wildly at friendlies and civilians. The public is outraged, and your funding drops further.
But you fight on, and you get lucky. You storm landed UFOs, capture enemy weapons, dissect alien corpses. The rookies that survive their first few missions turn into hardened veterans, and capable leaders. You start researching alien alloys, laser weapons, and power armor. You even manage to capture a few aliens alive, and begin interrogation. The aliens all have weaknesses, and you are beginning to learn how to kill them. You start learning about their plans for earth.
The aliens escalate their war. It's not just little gray men anymore. The aliens float, slither, and sprint across the ground at frightening speed. There are even rumors that some can control your mind. You discover alien bases on earth. But you fight back. You set up more bases around the world, upgrading your sensor systems until no UFO enters earth's atmosphere undetected. Your new interceptors with plasma cannons can outrun and challenge all but the most powerful alien ships.
But the aliens are incensed. They send new ships to hunt out XCOM bases. And when they do, they send a battleship at full speed for a direct assault. The aliens land in full force in your hangars, and you have to fight them up and down the corridors of your base. But now you have the upper hand. Your scientists have reverse-engineered all their technology, and your engineers are now manufacturing it for your own soldiers. You even sell the surplus to governments. Flush with cash, your now battle-hardened, psionically-resistant troops now regularly slaughter alien ships with ease. The most gifted among them can even mind-control aliens.
Finally, you launch an assault on the alien home-base itself...it's all or nothing.
(If I sound excited, it's because I am. If you're not excited, it's because I've failed to convey how awesome this game is.)
I look forward to sending Squaddie Dieter Esser into combat.
UPDATE: Xenonauts. This appears to be, according to previews and screenshots, a literal, nearly 100% accurate recreation of XCOM. So, it's going to be isometric 2D-sprite heaven, which is fine by me. Even the mission debrief screen looks like it uses the same font as XCOM. Holy shit. Dreams do come true. (Thanks to Loddigesia for letting me know)
UPDATE 2: Having looked into the Firaxis/2K remake a little more, dial down my enthusiasm from 11 to about 9. Apparently, only one XCOM base, only 4-6 soldiers in a squad, no base-defense missions, plus a quite a few gimmicky class-based special abilities. Makes the combat look a little LoL-ish. But still, an 80%-pure XCOM game would still be twice as good as any other squad-based tactical game. On the bright side, they seem to be building a great deal of mod-potential, so undiluted XCOM classic mod should be able to fix all that.
UPDATE 3: Bought Xenonauts. Mini-review here. Bottom line: In its current alpha-test form, it is a very-promising but very-limited game. You should buy only if you are a true X-COM fan, and want to support an XCOM remake.
UPDATE 4: Review Added.