There’s a genre of computer games called 4X (explore/expand/exploit/exterminate). well-known examples of which include the Civilization series and Master of Orion.
Ever wonder what the ur-progenitor of this genre was, the game at the root of 4X in the way Colossal Cave Adventure created the genre of dungeon-crawl games? It was Walter Bright’s game “Empire” from the early 1970s. You can read about it at his page on Classic Empire.
Since 1994 I’ve maintained an early Empire workalike written by Chuck Simmons in 1987 to run under the now-extinct VMS operating system; it was ported to Unix immediately, and remains to my best of knowledge the only open-source version or variant of Empire available.
Walter Bright does not acknowledge this version’s existence on his Empire page, which is fair because he didn’t write it and probably doesn’t consider it to be “Empire” at all. But it is close in gameplay and style to the earliest of Bright’s versions, except for being able to display its crude character-cell maps in color (I added that back when color terminals were cutting-edge technology).
If you love Civ or MOO, try this out for a look at what the computer 4X game was like before pixel graphics. The display and command interface are primitive by today’s standards, but the AI and general gameplay have held up surprisingly well. It’s instructive to see how many of the core tropes of later 4X games are already present in this one.
You can get version 1.10 of VMS-Empire here.