Portal is a text-driven adventure with a graphical interface published for the Amiga in 1986 by Activision. The writing is by American author Rob Swigart, and it was produced by Brad Fregger. Ports to the Commodore 64, Apple II, and IBM PC were later released. A version for the Atari ST was announced and developed, but not published. Until recently, it was thought that a Macintosh version was similarly developed yet left unpublished. The published Macintosh version was rediscovered in 2021 by a game collector.