X-COM: Terror From the Deep (1995)
Strategy

Publisher	MicroProse Software, Inc.
Developer	MicroProse Software, Inc.
Series	X-COM

Terror from the Deep (TFTD) on the surface is much like a skin change to UFO Defense. The game plays out the same way, equipment and enemies in TFTD are similar to the original, and all of the basic game mechanics are the same. However, the difficulty level has been substantially raised and there are a number of new features. Many of the third-party programs which modified, increased, or reduced the difficulty in the first X-COM game can also modify TFTD.

The motives of X-COM 2 being not much more than an X-COM 1 add-on can be best explained by quoting Mythos Games, developer of the original game:

"After completing UFO, MicroProse wanted to do a quick follow up within six months. We said that this was not feasible, and if it were possible it would be little more than the same game with different graphics. Instead we started work on X-COM: Apocalypse, which was much more ambitious. Once UFO/X-Com was clearly known to be a success, MicroProse suggested that we license the code for them to develop their own sequel. The rest is history."

In the original game, the player was tasked with defending Earth from alien invasion. Now, forty years after the first alien war, that lasted for three years, was won, a new alien menace begins to emerge from the deep oceans. The game plays out under water, with base-building and combat all being submerged beneath the waves. The only time in fact that the game moves onto dry land is for terror site missions, when the aliens attack a port, ship, or island holiday resort.

X-COM: TFTD, like the first game, consists of two parts. The GeoScape world view, a 3D map of the world used to track and intercept alien craft, and manage base facilities, research, manufacture, finance, etc. through a series of menus and sub-screens. The BattleScape engine is used for close personal combat between squads of aliens and humans, and takes the form of a turn based, isometric view, in which the player moves and fights with the aliens.