Mapster is an enhanced version of the Build Editor, the map editor

Level editor

A level editor is a software tool used to design levels, maps, campaigns, etc and virtual worlds for a video game. In some cases the creator of a video game releases an official level editor for a game, but other times the community of fans step in to fill the void...

 for computer games using the Build Engine

Build engine

The Build engine is a first-person shooter engine created by Ken Silverman for 3D Realms. Like the Doom engine, the Build engine represents its world on a two-dimensional grid using closed 2D shapes called sectors, and uses simple flat objects called sprites to populate the world geometry with...

, including Duke Nukem 3D

Duke Nukem 3D

Duke Nukem 3D is a first-person shooter computer game developed by 3D Realms and published by GT Interactive Software. The full version was released for the PC . It is a sequel to the platform games Duke Nukem and Duke Nukem II published by Apogee...

 and Shadow Warrior

Shadow Warrior

Shadow Warrior, often known by its initials SW, is a first-person shooter computer game developed by 3D Realms and released on May 13, 1997 by GT Interactive. Shadow Warrior was developed using Ken Silverman's Build engine and improved on 3D Realms' previous Build engine game, Duke Nukem 3D...

. Authored by Richard Gobeille (TerminX), it was built on Ken Silverman

Ken Silverman

Ken Silverman is a game programmer, best known for writing the Build engine used in Duke Nukem 3D, Shadow Warrior, Blood, and more than a dozen other games in the mid- to late-1990s...

's Build source release and re-added most of the features of Duke Build as well as some significant new ones.

Later TerminX also produced Mapster32 based on duke build and maintained as part of the EDuke32 codebase.

Notable Functions (as of Mapster32)

• Two additional grid sizes for extra precision
• Two modifier keys for smaller sector/sprite height increments
• Mass palette reference/visibility change
• Quick keyboard shortcut to save progress
• Free-roaming cursor in 3D mode
• Direct entry of sector/wall/sprite settings and positions
• Search for and go to sectors/walls/sprites with specified tags
• True Room over Room (TROR)