# X-COM: UFO Defense / Terror from the Deep — OpenXcom

Canonical: https://playable.wtf/games/openxcom-openxcom/

Project ID: project:openxcom-openxcom

A replacement engine for the original X-COM tactical strategy games.

## About this version

A replacement engine for the original X-COM tactical strategy games. The current website points downloads to OpenXcom Extended, a separate project. This entry preserves the original OpenXcom repository and is classified as source/build.

Source / build. Strategy.

[Build instructions](https://github.com/OpenXcom/OpenXcom)

## A campaign fought on two scales

In the original UFO Defense, defeating an alien squad is only part of your job. You also direct the organization that intercepts UFOs, researches recovered equipment and manufactures better weapons. Ground missions feed that strategic layer: bringing alien technology home creates opportunities that simply surviving a firefight does not.

That connection is the attraction for a player who likes decisions to matter beyond one battle. Spending resources and recovering useful material shape the tools available to your next squad. OpenXcom covers both UFO Defense and its separate sequel, Terror from the Deep; each needs its own original resources.

Sources: [X-COM: UFO Defense · publisher description](https://store.steampowered.com/app/7760/XCOM_UFO_Defense/) · [OpenXcom · README](https://raw.githubusercontent.com/OpenXcom/OpenXcom/HEAD/README.md)

## The original OpenXcom project

OpenXcom replaces the engine while reading the original games’ artwork and other resources. The source-build route here uses the original OpenXcom repository. OpenXcom Extended is a separate project, so a feature advertised for Extended should not be assumed to exist in this engine.

Customization is a substantial part of OpenXcom. Standard mods accompany the engine, and additional mods live in the user directory and are enabled through Options → Mods. Begin with an unmodified installation before adding a ruleset: the project specifically warns against using already altered XcomUtil data as the base.

Sources: [OpenXcom · README](https://raw.githubusercontent.com/OpenXcom/OpenXcom/HEAD/README.md)

## Keep game data and campaign files distinct

The engine separates original data, configuration and user files. UFO and TFTD resources belong in their corresponding data subdirectories, while the user directory holds saves, screenshots and installed mods. Keeping track of that user directory makes it easier to preserve a campaign when moving or rebuilding the engine.

Windows, macOS and Linux use different default locations, and command-line options can select explicit data, user and configuration folders. The README also explains a common mod-installation problem: an extra directory level inside an archive can hide its rules and terrain from the engine. Check the documented directory layout if an installed mod does not appear.

Sources: [OpenXcom · README](https://raw.githubusercontent.com/OpenXcom/OpenXcom/HEAD/README.md)

## Do I need the original game files?

Unmodified resources from UFO: Enemy Unknown (X-COM: UFO Defense) or X-COM: Terror from the Deep. Modded XcomUtil installations are not suitable base data.

Creator-reported: [Project guide](https://raw.githubusercontent.com/OpenXcom/OpenXcom/HEAD/README.md)

## How do I get started?

Build the OpenXcom engine using its platform instructions, then copy the UFO or TFTD resource folders into the matching data subdirectory.

Creator-reported: [Project guide](https://raw.githubusercontent.com/OpenXcom/OpenXcom/HEAD/README.md)

## Which devices and browsers work?

The source documents Windows, macOS and Linux builds.

Creator-reported: [Project guide](https://raw.githubusercontent.com/OpenXcom/OpenXcom/HEAD/README.md)

## What should I know before playing?

The current website points downloads to OpenXcom Extended, a separate project. This entry preserves the original OpenXcom repository and is classified as source/build.

Creator-reported: [Project guide](https://openxcom.org/downloads-milestones/)

## Credits and project

- [Original project](https://github.com/OpenXcom/OpenXcom)