OpenXcom

About

UFO: Enemy Unknown (X-COM: UFO Defense in North America) is a 1994 strategy game by Mythos Games and MicroProse that mixes base management with turn-based tactics; X-COM: Terror from the Deep (1995) is its sequel, set underwater. OpenXcom is a GPL-licensed open-source clone of UFO: Enemy Unknown and X-COM: Terror from the Deep, written in C++ with SDL. It runs on Windows, macOS and Linux using the original games' data files, and it is playable and still receives occasional updates.

How it differs from the original

It ships with a set of standard mods based on the classic XcomUtil and UFOExtender tools, and supports a large community mod scene through a dedicated mod portal.

Getting started

You need vanilla (unmodded) data files from either or both original games; if you own them on Steam, the Windows installer detects and copies them automatically. Mods go in a subfolder of the mods directory and are enabled from the in-game Options → Mods page.

Media

Additional notes

Warning

The project warns against using data from modded installs (e.g. with XcomUtil), which can cause bugs and crashes.