OpenXcom (clone of the X-COM/UFO series of games)

OpenXcom is an open-source clone of the popular "UFO: Enemy Unknown"
("X-COM: UFO Defense" in the USA release) and "X-COM: Terror From the
Deep" videogames by Microprose, licensed under the GPL and written in
C++ / SDL.

This is just a game engine. You will need the data files from
an installed copy of the original game. After the package is
installed, see: /usr/doc/OpenXcom-*/README.md