[2] Miller found that the standard shareware model was not viable for his games such as Beyond the Titanic (1986) and Supernova (1987), and beginning with Kroz the company pioneered the "Apogee model" of shareware distribution, wherein games were broken up into segments with the first part released for free to drive interest in the other monetized portions.
[1] In the 1990s, Apogee was best known for popularizing its shareware model and as the creator of franchises for MS-DOS on the personal computer such as Duke Nukem and as the publisher of games such as Commander Keen and Wolfenstein 3D.
[3] Also beginning in 1997, with their licensed Duke Nukem sequels, 3D Realms shifted from episodic MS-DOS titles to non-episodic console and personal computer games.
Several spinoff games and remakes, especially in the Duke Nukem series, have been created with 3D Realms granting a license but without serving as the developer or publisher.
In addition to these games, there are projects that were conceived but never began development, such as Dino Days (1991) and Commander Keen: The Universe is Toast!