The first-person shooter has since been traced as far back as Maze War, development of which began in 1973, and 1974's Spasim. After early, more playful titles like MIDI Maze in 1987, the genre coalesced into a more wantonly violent form with 1992's Wolfenstein 3D, which has been credited with creating the genre proper and the basic archetype upon which subsequent titles were based. One such title, and the progenitor of the genre's wider mainstream acceptance and popularity was Doom, perhaps one of the most influential games in this genre; for many years, the term Doom clone was used to designate this genre due to Doom's influence. 1998's Half-Life—along with its 2004 sequel Half-Life 2—enhanced the narrative and puzzle elements.[1][2] In 1999, Half-Life's mod Counter-Strike was released, and together with Doom is perhaps the most influential first-person shooters. GoldenEye 007 (1997) was a landmark first-person shooter for home consoles, while the Halo series heightened the console's commercial and critical appeal as a platform for first-person shooter titles. In the 21st century, the first-person shooter is the most commercially viable video game genre, and has more market share of any other genre in the gaming industry.