As you asked for a guide, I'll paste you my writeup
UFO: Enemy Unknown / XCOM - UFO Defense - A game guide
At
https://www.ufopaedia.org there is now a ton of information available about
the game. Most of the information in this guide also exist there, but here's
my version of what's important.
GAME OVERVIEW:
In the game you're administrating an organization, X-Com that is funded by many
countries around the world to save the world from the alien onslaught. The game
has a strategic bit where you build bases, research and manufacture and make
overall prioritizations of what to do. Early on, an important aspect is
ensuring you can detect alien activity, so you get the option of intercepting
it.
There's a small air-to-air combat minigame where you can shoot down UFO's. This
bit is not turn-based, but it's very simplistic and mostly depending on tech
levels and crafts as to who is winning. No fast reflexes needed.
Lastly, you can fly transports to sites where aliens are on the ground to
engage in land combat with them, or defend against aliens in your bases. The
land combat is where you will be spending most of your game time, and it is a
fairly complex turn based combat system. There's a lot of gear that can help
you here. You can research stuff that helps land combat, and your soldiers gain
individual experience and improve over time. Here, skill matters more than
tech. If you know what you are doing, most battles should be winnable with
pretty basic gear.
VERSIONS:
Released in Europe as "UFO: Enemy Unknown" and in US as "X-COM: UFO Defense" in
1994. There's a few different original versions, but all of them has quite a
few bugs, and today requires DOS emulation to play. Two different unofficial
products, UFOextender and XComUtil was created to try and fix bugs and improve.
These fan projects patches the game in various very configurable ways, but
reading and patching binary code is tricky, so they don't fix all the issues.
In 2010 a project called OpenXCom was started. This is a total reimplementation
of the game with more modern standards. It still uses and requires the original
game (I'm guessing to avoid copyright issues using the same graphics and sound
and the like), and this also requires you to have a working copy of the
original game to use it. Today, the orignal game is available cheaply on steam,
and openxcom automatically detects steam install from its installer. This seems
to be the simplest and best way of playing the game today, circumventing a lot
of known issues and exploits, and makes some quality of life improvements to
the game.
The OpenXCom version is pretty true to the orignal. The two biggest changes I
have encountered is that aliens seems more eager to exit their UFO and there's
no 80 item limit to troop transports, so to avoid infinite storage there, the
items in troop transports count towards base general storage capacity. Some of
the fixes makes a large impact on the game though, such as not having to pay
for dirt after altering your main base to be easier to defend. There are
various options, but the default options are typically closest to original
game. This is the version to play.
WINNING THE GAME:
To win the game, you need to capture some alien artifacts, research the most
critical ones, giving you the ability to research and build the ultimate craft.
Additionally, you need to capture and research live aliens, to figure out what
needs to be done. All of this is possible to do fairly quickly in game.
(Victory within April is certainly possible. I'm guessing also March if you
beeline hard enough.) If going for a speed game, you should know game mechanics
and the risks you are running. For this guide I'm mostly assuming you're taking
a safer route to victory, protecting Earth's citizens as best you can, and
delaying alien progress as best you can, while you get ready to permanently
stop the threat.
DETECTION:
If you don't detect the alien activity, you're missing out on so many levels.
Funding nations gets dissatisfied, you get less money from them, and might even
lose the game if they are sufficiently unhappy two months in a row.
Additionally you find less alien artifacts to sell for money (which is a huge
income boost), less alien artifacts to research, and less experience for your
soldiers. Conventional radars only have a few percent chance to detect an UFO
every 30 minutes. If you rely only on radars, on harder difficulties it is
fairly easy to lose the game due to bad score two months in a row, merely
because you didn't detect enough activity.
People around the world are reporting alien activity seen and you get a live
updated graph every 30 minutes. As alien activity lasts for many hours, you
are often able to intercept activity, even on the other side of the world, if
you notice it early. This can be used to counter limited radar capacity early
on, but it is very tedious to check graphs every 30 or 60 minutes to catch
activity early enough.
Your craft also detect alien presence fairly close to them, like moving radars
with a small range, but while the range isn't huge, you have a 100% chance of
detection every 30 minutes. An alternative to looking at the graphs all the
time is to have crafts patrolling areas where activity is likely. For this,
skyrangers are best as they can stay in the air for a long time. Alien
activity is typically limited to one or two zones for a given month, and after
you've detected what zones these are you can patrol.
Radar is so much simpler though, so building more bases to get radar coverage
around the world is an early priority. There's alien tech for improved radar
that is awesome and available early if you know what to do. If you know how to,
you can skip building conventional radars until you have it available.
SHOOTING DOWN UFOS:
To shoot down UFOs you use crafts with mounted weapons like the starting
interceptor. However, if you shoot down a UFO, you will destroy parts of it,
and you will likely face less aliens and get less loot when attacking it. If
you can handle the UFOs coming at you, you're better of waiting until it lands
and fight it on the ground. There are three exceptions. You may want to avoid
a night mission, and shooting it down, means you get a crash site which is
available long enough so you can await sunlight. Secondly, it is hard to save
civilians in terror missions without endangering your own soldiers. Also, there
is no UFO in those missions so you are missing out on all the UFO loot. If you
can, these are better to shoot down. Thirdly, shooting down a UFO will trigger
a chance for alien retaliation against one of your bases, and will also delay
the next UFO on that mission, so you can shoot it down, if you want to provoke
either.
What craft you have matters less than what weapons you use. Plasma Beams are
king. They have large range and shoot fast. Meaning you can take down most UFOs
at a range where they can't damage you. Interceptors with Avalanche launchers
have even larger range, and can also be used safely against everything but
battleships, but as the ammo is very limited you need multiple crafts to
engage. Alien UFOs move fast, and sometimes they just fly away too fast. In
these instances a more modern craft with higher speed is nice, but usually
this isn't an issue against anything bigger than a very small UFO. Also less
of an issue when using craft weapons with high range.
Battleships are hard to shoot down. They can cause massive damage and can't
be hurt before you're in range of its weapons. Think twice before deciding
that it is worth engaging it.
LAND COMBAT:
The real combat happens when your soldiers come up against the aliens in the
turn based land combat system. There's many types of gear available giving you
many different tactical possibilities. Your soldiers are good at different
things, and they get experience for successful actions, so you should try to
keep them alive.
To begin with you only have conventional weapons. This works out ok against
Sectoids and Floaters which you are likely to face in the beginning, but
becomes really tricky when you face terror units or better armored alien
races. I would recommend researching laser rifles quickly and make them your
main weapon. It has good accuracy, unlimited ammo, can be fired fairly quickly
and can kill anything in the game (though tougher units may require many hits).
It also doesn't cost you Elerium which the alien weapons typically do.
Armor for your soldiers help a lot for their survival. Especially power suits
and flying suits give you a decent chance to survive a plasma hit, and with a
medikit available, you can save most of those who survive the first hit. Personal
armor also helps, but combined with the low health your units likely have early
on, your chance of surviving a hit with it is still low.
Night missions are terribly, in that aliens can still spot you 20 tiles away,
while you can only spot them 9 tiles away unless you have a light source
lighting them up. Use flares for this. Ensure you have flares lighting up
anything in a 20 tile distance from your troops. This is tedious so try to
fight during daytime to avoid the alien advantage.
Smoke grenades are big life savers. Arm at least one before the mission start.
(Right clicking in inventory screen) If you have aliens looking into your
skyranger on turn 1, you can drop it on the floor and get smoke on level 1,
likely meaning the aliens won't see you in their first turn. You can also throw
one outside, and wait a turn to get smoke there, so when you step down you avoid
reaction fires from angles you can't check before you exit.
The basic survival recipy is:
- If you spot the alien at the same time it spots you, there is mutual
surprise and it doesn't get to do any reaction fire. Use this to spot an
alien someone else can kill. Aliens cannot react to agents acting outside
its visual range. (And try to avoid walking past a corner such that an
alien can see you while you can't see it, as it may reaction fire and kill
you.)
- If you end your turn close to aliens, you can have bad luck and it may come
straight for you and shoot you. To stay safe, you need to establish a gap
between your forces and the alien forces, so walking across the gap means
they don't have enough TU left to shoot you. Mutual surprise works for
aliens too, so if they spot you the same time, they will get first shot in
their turn. This gap can be established by having spotters move towards
potential alien positions in your turn, and then move back or hide
afterwards. Smoke grenades can be used to increase visibility gap if there
is no suitable terrain to do it close by.
- Aliens will never shoot at a soldier it doesn't have line of sight to. They
never intentionally shoot at terrain to see what's on the other side, and
they don't share target information between themselves. (With the exception
of PSI attacks)
- You have an infinite amount of turns, so you don't need to rush anything,
unless on a terror mission where you want to save civilians.
- Aliens cannot react to you turning in place, so if you have moved through
a door or around a corner and haven't been shot, you can safely look around.
However, once you end up doing anything else, you will have lower TU, making
it more likely that aliens can react. (To get a reaction shot in opponents
turn you have to have better modified reaction than the opponent, your
reaction is modified by your remaining TU)
- As far as I know, if you are spotting an alien, and can move out of sight
of it by moving one tile, that alien can't react to that as he need to react
to the target square, not the source.
Always surviving is still hard though. Especially as the best tactic to save
soldiers is very tedious, so you're likely to take some chances to speed things
up. It's pretty impossible to safely invade the insides of a UFO for instance.
It is good practice to have some expendable soldiers in the front of the
transport, and let them be the ones taking the risk of being closest to the
aliens.
Psionics make land combat trivial. When you can mind control the aliens, you
can just spot one, control it, make it drop their weapons so they're never a
threat again, and then use it to spot more and rince and repeat. Aliens using
psionics against you can be avoided late game by not using soldiers with weak
psionic strength/skill. Early game, using laser weapons and power/flying suits
works out pretty good, as a mind controlled soldier is unlikely to kill a
fellow soldier.
