

With one third of the game (nine levels) distributed as shareware, Doom was played by an estimated 10 million people within two years of its release, popularizing the mode of gameplay and spawning a gaming subculture as a sign of its effect on the industry, games from the years 1994-1997 boom of first-person shooters are often known simply as "Doom clones". The Ultimate Doom, an updated release of the original game featuring the fourth episode, came out in 1995. The game is divided into three nine-level episodes. In Doom, players assume the role of a space marine, popularly known as "Doomguy", who must fight his way through the hordes of invading demons from Hell.

Doom (typeset as DOOM in official documents) is a 1993 science fiction horror-themed first-person shooter video game by id Software.
