Wolfenstein 3D is the video game which started the first person shooter genre on the PC; it was created by ID Software and published by Apogee in 1992. In the game, the player is a soldier attempting to escape from a Nazi building; there are many guards with pistols and machine guns about, as well as attack dogs. The building has a number of hidden passages containing various treasures, food supplies, and medical kits, as well as various guns and ammunition.
Wolfenstein 3D was originally released as shareware, which allowed it to be copied widely. The shareware release contained 1 episode, consisting of 10 missions (levels). The commercial release consisted of 6 episodes, including the shareware episode. Each episode had a different "boss" which had to be killed in the final mission in order to complete the episode. In order to complete an episode, only 9 of the 10 missions needed to be completed. Hidden in one of the first eight missions was an entrance to a secret level.
An expansion pack, Spear Of Destiny, was also released.
To render the walls in pseudo-3D, the game used ray casting, a special case of ray tracing that sent out one ray for each column of pixels, checked if it intersected a wall, and drew textures on the screen accordingly, creating a depth buffer against which to clip the scaled sprites that represented enemies, powerups, and props.
A new first-person shooter, Return To Castle Wolfenstein, a loose sequel (though with the advance of technology the graphics and gameplay are vastly different), has been released. It uses the Quake III Arena graphics engine.