What is X-COM?
X-Com is a simulation of an alien invasion of earth. It is composed of two parts.
In part 1, you are focused on globe-level activities: Tracking UFO actions around the world (possibly shooting them down, or sending troops to the sites of ship landings), keeping governments happy with your actions, getting funding money from various governments, and spending it on soldiers and equipment.
In part 2, you are in a turn-based, tactical, grid-based combat simulation, with fog-of-war; your goal is generally to defeat (capture or kill) the aliens in that battle. More accurately, you are scored based on a variety of functions (aliens killed, innocent bystanders killed, etc), and your goal is to be positive. It is possible to have to flee but still have positive points (considered a marginal victory -- you might not have stopped the aliens, but you did enough damage that your funding nations will be happy enough).
Most, but not all, of these battles will involve an alien ship, either intact or damaged.
The overall gameplay alternates between globe-level, and single-battlefield level, until either your forces are completely wiped out, or you have defeated the enemy invasion.
What is OpenXcom?
OpenXcom is an open-source clone of the original X-COM, licensed under the GPL and written in C++ / SDL. It was originally founded by SupSuper in February 2009, and has since grown into a small development team surrounded by a very supporting community.
The goal of the project is to bring back the tried and true feel of the original with none of the issues. All the same graphics, sound and gameplay with a brand new codebase written from scratch. This should give it:
- Fixability: Play the game natively without any need for emulators or fancy hacks, with none of the limitations and bugs that plagued the original. No more 80-item-limit, personnel limits, funding overflows, disconnected facilities, broken proximity grenades, floating soldiers, etc.
- Moddability: Tweak the game to your heart's content. Sure the original was pretty good, but maybe you just think it could be that bit better. A nicer base layout, better laser weapons, maybe challenge yourself with a custom game mode, or just put in all the crazy stuff you've always wanted! None of it is hardcoded. See Mods (OpenXcom)
- Flexibility: Port the game to any platform you like, customize it to your liking, or use it to make your own far-fetched remakes. The code is fully documented and open-source so anyone can take a crack at it.
OXC and beyond
You probably want to use OpenXcom with mods. This involves much less frustration when you understand basics of mod compatibility. Any mod may have one of 3 distinct engines as a requirement: pure OXC, "Nightly" OXC or OXCE. They are backward compatible, in general. For example, Hybrid Mod (which combines X-COM and TFTD) or X-Com Files require OXCE. See also Installing (OpenXcom) and Mods (OpenXcom).
There are many mods. Fortunately, it’s not a complete mess. Metadata file included in the new path structure (Nightly and OXCE) allows mods to specify the required version of the engine, if any, and master ruleset - normally xcom1 (EU) or xcom2 (TFTD), but sometimes another mod (which may have its own master ruleset in turn). In the mod setup page of Nightly or OXCE a drop-down list chooses the master, and only mods under that master are displayed; so if you chose UFO: EU, the list is not cluttered with mods relevant only to TFTD or X-Com Files, or vice versa.
- Plain old OXC: the proper, stable release version. Updated approximately once per forever. Has few mods beyond improved resources (such as better sprites or sounds) or simple rebalance. If you want to play vanilla or mostly-vanilla, it's quite good.
- OXC Nightly: as the name implies, it's a development/modding branch regularly compiled from its official repository. Bug fixes can be applied quickly, the rest seems to seep from OXCE very slowly. Thus it’s a more stable branch lagging far behind OXCE. It has the directory structure reworked, mod metadata file (metadata.yml) is required.
- OpenXcom Extended, aka OXCE: a cutting edge development branch of OpenXcom ahead of Nightly. Has some nice improvements (such as previews and Motion Scanner memory), but mostly it’s about modding.
- It’s generally backward compatible with OXC, which is backward compatible with the original, but some things look more like bugs or engine limitations than features. Differences in game mechanics are described here.
- Many features are moved from hardcoded to available for modding, some new features are added (accessible via mods). Since it's a very fresh development version, there's some risk that modding "language" may change in future. Some highlights of less-arcane modding capabilities:
- Base Facilities: Facilities destroyed by raids or bombardment turn into default rubble “buildings”, thus the base is not necessarily disconnected. Specific types specify tiles where stored items are spawned in battlescape, subtype for Alien Containment (with corresponding value on specific aliens — air breathers vs. aquatic, or you could start a Silacoid farm, but containment for these things cannot be the same as for floaters), type and amount of ammunition for Base Defence (even Avalanches cost money and storage space, never mind Fusion Ball Defences/P.W.T. Defences), soldier recovery bonuses (build a hospital), etc. Likelihood of taking a hit from bombardment (hangars, defenses and radars can be set to more likely destruction than underground barracks). Base services required to build/provided/blocked: these serve as prerequisites for other elements; e.g. the player would need an advanced surgery facility plus research to install implants, kennels to keep dogs, specialized facilities required for research or manufacture (e.g.: Psi Amp could be made in Workshop as usual, but need a working Psi Lab at the same base), etc. Facilities can have custom rubble and list of facilities that can be built over them (i.e. upgraded to). Simple example: Improved Living Quarters & Large Stores mod adds two facilities that are 2×2 sized, but more space-efficient. Slightly more complex: Recruitment Office mod (needs Building Mod Pack, and see the comments) provides a facility that allows to hire pre-screened soldiers (custom Soldier Types with better stats at a greater salary), and after extra research can be upgraded to support psionic screening.
- Cost of use (TU, energy and/or anything else), action menu texts and messages (if any) for all actions with specific items can be customized.
- Weapons can have power reduced by range at arbitrary rate. Ammunition expended per shot in each firing mode is customizable. Adjustments to accuracy and damage from arbitrary combination of stats. Accuracy adjustments for kneeling, for one-handed use of two-handed weapons, for shooting without line of sight to the target and for CQC (point blank shots) can be set globally and overridden per weapon.
- Shotguns. Nightly already allows them, but the only new parameter is number of pellets in a round of ammunition. OXCE can treat it as a single spread shot rather than independent simultaneous shots, set relative spread and choose the distribution (evenly or grouping).
- Spray targeting mode: if enabled for a given weapon, in auto fire mode Ctrl+Shift+LMB starts picking numbered waypoints; after the last one, firing starts, but now the unit will move its aim trying to evenly distribute hits along this path, rather than aiming at the same spot.
- Firing modes can be customized, too. A double-barreled shotgun can be implemented by having "auto fire" mode set to 2 shots and renamed. Up to 4 ammunition slots with their own load/unload costs and compatibility lists, selected per mode — for underslung grenade launchers, etc.
- Damage modes are customizable for a specific weapon (or template). Example: if you want High Explosive pack to breach UFO walls, in OXC this can be done by setting its power to 200 (standard mod XcomUtil High Explosive Damage does this, along with limiting blast radius to 10). In OXCE the same can be also accomplished by setting its damage rate to tiles at 0.92, or power to 200, but rather than capping blast radius directly, doubled RadiusReduction (damage won’t go abruptly from half to none at the edge of blast area).
- Not only built-in weapons, like tank turrets, but special weapons that can be used with an empty hand (like punching). Items that spawn units - something like Brainsucker Launcher or small drone.
- Melee dodge, also used for shots in close quarters combat mode. Sneaking upon the target allows to penalize dodge or avoid CQC entirety (the attacker just stabs or caps an unaware enemy without much hassle); specific unit types may be immune to sneaking, or not have CQC mode at all. As shots with CQC adjustments can be balanced differently from generic shots, less-agile weapons can be given disadvantages, making pistols/SMG/sawn-off shotguns good at shooting fast enemies point blank, and sniper rifles unsuitable for the same purpose despite otherwise great accuracy. X-Com Files has accuracy in Close Quarters 133 for most pistols (up to 165 in some cases), 120 for most SMG, 90-120 for shotguns (150 for sawed-off), 100 for most rifles, 45-80 for sniper rifles, and 45-60 for most heavy weapons (28 in one case).
- Grenade functionality is split and customizable.
- Fuses are now per-item, rather than either timer dial from the original game (rarely used beyond "0" anyway) or “Instant Grenades” option for all. It’s possible to have timer on High Explosive pack, while normal grenades just go off after the throw or at the end of that turn.
- Items can be primed and un-primed, if configured this way. Mostly applies to grenades, but can be done with flares. Or as an arbitrary switch or action for any other item (with some scripting).
- Fuses can be allowed to go off while in equipment, if you want to acknowledge the unpleasant fact that timer on a demolition charge is ticking whether someone holds it tight or not,
- Soldiers: now there are different soldier types that can be assigned different stats, etc (for example: common soldiers, pilots and dogs). Each with separate parameters such as default armor (pilots have flight suit as default armor, dogs have “armor” with dog stats and cannot wear human armor), required base functionality (dogs need kennels), hiring cost, how many can be hired per month (it’s easier to find a handful of healthy dogs than pilots), salary and promotions (pilots have their own ranks, while dogs don’t use any), score value and multiplier for morale loss when this unit is killed (drones and cameras may have 0), special weapons (dog may get by with bite weapon defined in armor section, but hybrid soldiers could have a built-in psi weapon with statistics different from psiamp just like some aliens have, martial artists an extra punch etc) separate from armor. And a few odd properties like “allowPiloting” and experience gain from dogfights.
- Soldier "transformations", with very detailed prerequisites (usually includes the same transformation not applied earlier), which can mean anything from taking time for special training giving a few stat bonuses to cyborgization. X-Com Files has "Martial Arts Training", "Combat Pilot Training" and some fancy implants.
- Soldier Bonuses, from transformations or commendations/medals.
- Aircraft now have shield stats. May have built-in weapons. Tractor beams can prevent the opponent from running away, or even force crash-landing on its own.
- May require pilots; pilots’ Firing Accuracy affects attacks, Reaction affects defense and Bravery affects approach speed (specifics are adjustable). Dogfights can give experience bonus to the stats as defined in ruleset. The pilots are also present on missions, thus can raise stats the usual way. For a demonstration, see Top Gun mod.
- Each Craft weapon has type, each slot has set of types allowed, e.g. gun mounts are for cannons, pylons are for missiles. Since "craft weapons" now can alter stats, they may be arbitrary upgrades. X-Com Files has shield generator, afterburner, maneuver thrusters, extra fuel tanks and radar enhancements.
- Retaliation missions against X-Com bases may be airstrikes, rather than ground assault. If not shot down, they’ll bombard — may be set to nuke the whole base outright or destroy random facilities (that’s also customizable, but the Access Lift survives except in “entire base” variant).
- Aliens can launch interceptors when you go for their base. For a demonstration, see Alien Hives mod.
- Alien races may have adjustments to attack/weapon power/evasion/detection range/etc. Or have unusual crew rosters and loadouts. Also, unmanned UFO that fight to 0% rather than 50% and as such never crash land (you still thwart their mission and get score for destruction).
- Improved particle system, now allows separate parameters in air and underwater. For a demonstration see Hyper & Trajectory mod - projectile speeds are set very high, bursts cycle quickly, but while you can't see bullets like in the original X-Com, they leave trails of dots.
- Allows scripting, which opens new and wide fields for modding above and beyond those covered in the ruleset capabilities.
- Hatching Chryssalids and Tentaculats mod: "Eggs injected by Chryssalids do not kill the soldiers instantly. Eggs can be removed with a Cure" (cure requires some research).
- X-Com Files include handcuffs, flashbangs (not mere stun damage, scripted support of "dazed" status effect and "flashbang resistance" variable assigned to every critter/armor in the mod) and regenerating personal shields.
- X-Com Files Arsenal Additions include things like gas masks. And riot shields that can be wielded or discarded (and fall apart after certain amount of damage).
- Soldier Skills are custom scripted actions used via special menu or generic item action; a list is enabled for soldier type, with set conditions including specific Bonus, specific Items (in hands or equipment), action performed, etc; looks promising, but no released mod uses them yet.
The OpenXcom past, present and future development history
|0.1||October 17th, 2010||
|0.2||January 28th, 2011||
|0.3||September 1st, 2011||
|0.4||August 14th, 2012||
|0.45||November 5, 2012||
|0.9||May 7, 2013||
|1.0||June 13, 2014||