X-COM (also X-COM: First Alien Invasion[2]) was part of a budget range video game series released in 1999 by Hasbro Interactive for Microsoft Windows that relied solely on the play-by-mail concept.

On each map there are a number of crates containing powerups (such as doubling the action points, damage or range of a unit for a turn, reveal the complete map for the same turn, instantly heal the unit, or provide a shield, landmine or grenades), but also hazards such as mines and traps or teleports.

Unit and weapon design is based on the first game of the series, UFO-Enemy Unknown, except the human flame-thrower and sniper's rifle and the alien helium thrower (the manual states the game has "a wide variety of weapons all from the year 2001", while UFO-EU starts in 1999).

Each unit is tied to a weapon; it isn't possible, for instance, to equip a Commander with a rocket launcher instead of the sniper's rifle.

The game is played in a simplified logic of the older games: each unit "life" is measured by hit points and can only move a certain number of squares depending on their action points.