First things first, I have played the original on PC several times and could not wait to see how this one would turn out. Sadly, it fails on a few levels with respect to the original, however that is not to say it is a bad game. There are a few welcomed changes, but some of the omissions are what causes my heartstrings to be pulled.
You are the commander of XCOM, a multinational organization that has been put together to try and quell the recent alien outbreak on earth. Your responsibilities are to direct the research teams, instruct your engineers on what they should manufacture/build, and manage and hire a team of soldiers. In the midst of all of this, you are required to keep panic levels down across the globe in order to keep nations funding your effort against the alien invasion.
There is a tutorial mission or two at the beginning to get you started, but the tutorial missions are really boring because they basically force you to move to specific spots, but if you have never played a turn based strategy game before, or are just wanting to get a handle on the game mechanics, it is probably a good idea to be shoved along through it. One benefit to going through it as opposed to skipping it is the reward of a promoted soldier.
Once you get the first research project and engineer build underway, the training wheels come off and you are allowed to manage things on your own. It is tempting to use up all of your funds on facilities for your base right away, but you may find yourself wishing you had saved some of the funds for other things if you spend too hastily. Sadly, there is only one base to manage unlike the original, and you get a bonus depending on which continent you decide to build your base of operations. Also absent from this installment is the possibility of an alien attack on your base. However, it isn't such a bad thing because in the original game, typically your second base would get the hand-me-downs as far as soldiers and equipment anyway, so having just one base isn't as bad as it may seem. Some of you may have tried to split your forces more evenly, but when crises arise, having only 1/2 of your best soldiers and gear to fill a Skyranger is a scary thought.
Researching alien tech and performing alien autopsies is paramount if you are to sway the odds back in XCOM's favor since they have more advanced weaponry and armor, not to mention you are almost always outnumbered. This brings me to mentioning the squad size limit of 4 at the beginning of the game, but you can buy upgrades to your squad size at the officer training facility which is a build option for your base. Starting on normal, this building is already constructed, but on Classic and above, you must build it on your own. I was not very fond of the small squad size when I first read about it because of how easy it is for your soldiers to get their asses handed to them in the original, especially rookies. I believe the squad size limit in the original was 12 on a Skyranger, and bringing that many was often necessary to overcome the odds, especially in the beginning. However, having such a small squad isn't as big a detraction as it may seem since your soldiers have abilities that they can use depending on the promotions and class that they possess.
Intercepting ufos is somewhat of a lackluster affair. In probably over 100 missions played, I think I only had the chance to down about 12 ufos. This is probably due to the limited number of missions (70 I believe), so there cannot be a huge variety of crash sites to investigate since this game doesn't have the same randomness of the original. You can upgrade your interceptors loadout with heavier weapons, and can also buy a tracking, aim, and dodge upgrade to use in the little mini game that launches during an interception. There is also an improved interceptor that can be purchased upon researching some alien tech. Although you only have the one base, you can station interceptors on each continent in order to be able to respond to a threat wherever it may arise.
Time units and crouching are gone in favor of a cover system. I was open to the change, and it works, but it does have it's downside. Rather than managing time units and being able to stock your belt, backpack and leg straps, you are only granted 2 moves, and are only given one backpack slot as well as a sidearm/rocket, main weapon, and armor. My biggest issue with the two turn mechanics is that if you make your first move just slightly outside of the blue 1 turn boundary, your soldier has automatically dashed there and cannot use any further action (barring special class skills such as Run and Gun for the assault class). If time units were present, you would still have left over time to at least pull off a poor accuracy shot, but the new system does not accommodate this.
The cover system shows you a 1/2 shield when you are about to move to half cover, and full shield when you are going to move to heavy cover, and if the shield is red you are in no cover. I don't mind the cover system all that much, but it does somewhat force your hand as to where on the map you should move. Also, it seems as though the aliens have a much better chance to hit you when you are in cover, as opposed to when they are. It is not uncommon to miss shots that say you have 85% to hit (I've even missed a couple 96% shots) and rarely do you connect on anything less than 50% even though the percentages imply that you should hit 1/2 the time.
Building certain types of buildings adjacent to one another if they are of the same type grants you small bonuses, and you have to plan accordingly for power, lab space, and workshop space, all the while keeping enough satellite uplinks available in order to maintain satellites above the countries that are part of the council if you want to keep them funding you, and the panic level down in that area. You will most likely not be able to keep all of the nations involved since you don't have the assets required at the beginning, so don't fret if one or 2 nations drop off of the council in the first month or 2. It is important to launch satellites over nations that are near the breaking point, or if there is no imminent danger of a council nation dropping out, launching a satellite above a nation that will provide more income makes the most sense. There are also bonuses for having satellite coverage over every council nation on one continent. You will lose the game should you lose 8 or more nations, but that is probably not very likely unless this is just not your type of game.
The mission types include city invasions, ufo landings, ufo crash sites (should you intercept and shoot one down), bomb defusal, and escort/rescue missions. They are all slightly varied enough encounters to keep you somewhat entertained, but if you play enough missions, you will get repeat missions, ans sadly the enemy positions are always the same if you recognize the map. City invasion maps require you to try and rescue as many civilians as you can before they are killed by the aliens, and the more you rescue, the larger the panic level decrease you are provided for that nation. Without trying to spoil to much, there is a particular alien that makes these levels very difficult until you have a decent squad and gear because they don't just kill civilians, they turn them against you! Ufo landings are just what the name suggests, a ufo lands, and you must send in the squad to investigate. A crash site is no different than a landing other than the fact that some of the ufo's equipment will most likely be damaged unless you shot it down with an upgraded EMP weapon for your interceptor. Bomb defusal missions can be rather annoying because you are forced to rush and switch off power nodes to extend the number of turns before the bomb blows, but this forces you to be much more aggressive and at times compromise the safety of your troops. And finally the escort/rescue missions usually just require you to find some high value individual and bring them back to the skyranger.
There are only 4 class types, including sniper, support, heavy, and assault. When your rookie soldier gets promoted, they are randomly assigned a class type, but from there you can choose between different class skills after each promotion. It is disappointing that you cannot decide which class the soldier gets promoted to, because there will come a time when you are in need of a particular class, and you just have to hope that upon promotion, you get the one you so desire. Each class has special abilities that are beneficial, so taking at least one of each class into a battle is a good idea. You can purchase an upgrade which allows all soldiers that are hired to have already earned their first promotion which makes life much easier. You no longer have to trudge rookies out into the field and not only hope they survive, but hope they acquire the appropriate class promotion. When your soldiers gain ranks, not only do they gain more perks, but they are also less likely to panic when faced with adversity due to a higher will capacity.
Once you have upgraded your soldiers ranks, and have researched everything there is to research, the game becomes very easy on normal. You may be tempted to go back and revert to a previous save whenever your favorite soldiers die, but if you chose to play on "Iron Man" mode, there is no such luck. Dead soldiers are dead as they come. Classic is pretty brutal, but it may be more suitable to you if you like a challenge. I did not dare go above that since classic kicked my butt the first hour or so. Still, playing on normal provides a slight challenge, but it pales in comparison to the original when it comes to difficulty on normal.
There are a few bugs here and there, but they aren't overwhelmingly prevalent to the point of frustration, though they are evident enough to merit notice. Scaling the map to different heights sometimes causes cursor convulsions and building transparency to flutter. Occasionally there are freezes for no apparent reason, and I even had a soldier get stuck in the ceiling after using the jetpack on the archangel armor. The cursor will wobble back and forth at times and when it does, you may find yourself moving a soldier where you did not intend because of it. Also at times when you blast an alien off of a ledge, the camera will pan down to an apparent abyss where all you see is black, then when he hits an invisible floor, the camera pans back up again. There might be a couple others that I am forgetting, or that I haven't experienced, but there are bugs.
Overall, the game is good, but other than a difficulty swap, there isn't a whole lot of replay value. The original was so varied and random that no 2 playthroughs are alike, but the missions in this installment don't lend themselves very well to more than 2 plays. The cover system feels a bit broken, and the small squad size is disappointing though it doesn't detract from the game as much as it could have had the maps been bigger and more random. It is still a good representation of the original in many respects, and is worth playing, but I wouldn't count on this game keeping you busy through the holidays. A pretty stellar effort, but it could have been so much more.