High Quality Content by WIKIPEDIA articles! X-COM: Terror from the Deep is a computer game, the sequel to UFO: Enemy Unknown (or X-COM: UFO Defense in North America), and the second part of the X-COM series. It was developed and published by MicroProse. Its interface is nearly identical to its predecessor, as is its graphics technology. 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.