3D Realms

3D Realms Entertainment ApS is a video game publisher based in Aalborg, Denmark. Scott Miller founded the company in his parents' home in Garland, Texas (US) in 1987 as Apogee Software Productions, to release his game Kingdom of Kroz. In the late 1980s and early 1990s, the company popularized a distribution model where each game consists of three episodes, with the first given away free as shareware and the other two available for purchase. Duke Nukem was a major franchise created by Apogee to use this model, and Apogee published Commander Keen and Wolfenstein 3D the same way.

Apogee adopted the trading name 3D Realms in 1996; the "Apogee Software" name and logo were sold to Terry Nagy in 2008, using which he established Apogee Entertainment. While Apogee focused on 2D platform games and puzzle games, 3D Realms produced fully 3D games and moved away from shareware distribution.