"Doom" was influential and dozens of new first-person shooter games appeared following "Doom"s release, often referred to as ""Doom" clones". The term was initially popular, and after 1996, gradually replaced by "first-person shooter", which had firmly superseded around 1998. Some of these were cheap clones, hastily assembled and quickly forgotten, and others explored new grounds of the genre with high acclaim. Many of "Doom"s closely imitated features include the selection of weapons and cheat codes. Some successors include Apogee's "Rise of the Triad" (based on the "Wolfenstein 3D" engine) and Looking Glass Studios's "System Shock". The popularity of "Star Wars"-themed WADs is rumored to have been the factor that prompted LucasArts to create their first-person shooter "Dark Forces".