Portal is a mix between a computerized novel and an interactive game. It was published for the Amiga in 1986 by Activision, written by Rob Swigart, produced by Brad Fregger, and programmed by Nexa Corporation. Versions for the Commodore 64, Apple II, and DOS were later released. Versions for the Macintosh and Atari ST were announced and developed, but never formally released.