Page "Development of Doom" Paragraph 8

Some of the ideas from the Doom Bible, though discarded for Doom, showed up in later games.

Instead of employing separate levels, Doom was initially supposed to use a hub system to enable a large, continuous world ; in the game, the different areas would be connected by a monorail.

Hubs were later used in id Software's Quake II, Doom RPG and Raven Software's Hexen.

Monorails also make an appearance in Doom 3, although not as a Hub system.

The game would include interactive computer terminals ; this first appeared in Doom 3.

Tom Hall additionally used concepts from the Doom Bible in Rise of the Triad and Terminal Velocity, which he designed after leaving id Software for Apogee and 3D Realms.

Also, a laser weapon referred to as " the Unmaker " in the Doom Bible made its only appearance in Doom 64.