Room-over-room

Room-over-room is a term used to describe placing a room directly above another, often used in reference to id Softwares "Doom" series. In the original "Doom" games, all mapping was done in 2D while height variance was done via numbers so getting the effect to work was an achievement at the time. In true 3D engines, such as the Quake engine, this is an easy effect to pull off.

The restriction was originally solved by using a silent transport to fake the effect, but has since been completely corrected in some source ports, such as Doom Legacy. In game engines such as "Cube", room-over-room can be mimicked using 3D models.