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, 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.