The early history of game design was basically one of computer game addicts who learned to write code so that they could alter the games they were playing, then progressed to writing code creating new levels (or “maps”) for existing games, to working on original product. Somewhere along that line, if they were lucky, they connected with a computer game company.
As the industry has matured, so has the process of training game developers. The games have gotten much more complex as computers have become more powerful. Not necessarily more complex in plot, but complex in terms of what is required to put the images on the screen and to create the interaction sequences. Color and shadowing have become much more realistic as have human (and inhuman) figures. The games have progressed from flat, single dimensional sequences to scenes with depth that are rendered in two and three dimensions.