Editing Doom engine (section)

===Sectors===
Each sector contains a number of properties: a floor height, ceiling height, light level, a floor [[Texture mapping|texture]] and a ceiling texture. To have a different light level in a particular area, for example, a new sector must be created for that area with a different light level. One-sided linedefs therefore represent solid walls, while two-sided linedefs represent bridge lines between sectors.