"Descent is a 3D first-person shooter video game developed by Parallax Software and released by Interplay Entertainment Corp. in 1995. The game features six degrees of freedom gameplay and garnered several expansion packs. It spawned two direct sequels: Descent II and Descent 3. The trademark for Descent was allowed to lapse by Interplay in 2002 and was re-registered in 2008. " Source: Wikipedia, "Descent_(video_game)," available under the CC-BY-SA License.