Game Development Dictionary
A game released in 1995 by Interplay Productions and Parallax Software, Descent was the first commercial game to feature full 6-degrees-of-freedom movement inside a structure. The player's objective is to destory haywire mining robots, save hostages, destroy the mine's reactor and escape before it blows the whole mine to kingdom come. Descent also features an excellent enemy AI which learns the player's combat style, forcing him to change his tactics or die. Interplay has since released two sequels to this popular game.