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. A unique game for its time, Portal was one part text-driven adventure (à la Zork or Planetfall) but with a graphical interface.
The player, taking on the role of the unnamed astronaut protagonist, returns from a failed 100 year voyage to 61 Cygni to find the Earth devoid of humans. Cars are rusted and covered with moss, the streets are completely barren and everything appears as though the entire human race had just vanished suddenly. The player happens upon a barely functioning computer terminal that is tied into a storytelling mainframe, Homer. Through this interface, the player, assisted by Homer who attempts to weave the information into a coherent narrative, discovers information in order to piece together the occurrences leading to the disappearance of the human race. For instance, spending some time in the Medical Records section may unlock a piece of data in the Science section, and through these links the player can finish the game.
A review in Computer Gaming World described the story as "interesting and well-written", but felt the interface was tedious. The Amiga version, using a mouse, was considered superior to that of the C64, and only bothered the reviewer by way of slowing down the reading of the story.
A hardcover novel, titled Portal: A Dataspace Retrieval and composed mostly of the text from the interactive novel with some new additions, was written by the same author, Rob Swigart and first published by St. Martin's Press in 1988. It takes the form of a series of notes on different subjects, in an order that the player would encounter them through Homer. A softcover edition was released by Backinprint.com in 2001.
An eBook was released "under the Creative Commons BY-NC-ND Unported license 3.0". The author has allowed it to be uploaded to the MobileRead forum.
In April 2012, author Rob Swigart and Subliminal Games launched a Kickstarter fundraising campaign called "Rob Swigart's Portal (1986) Reborn" to recreate the world of Portal as a modern third-person adventure game. Some of the features set to be included: moving backward or forward in time through a simulation of the past and changing the character's appearance for different responses and reactions by virtual non-player characters. The Kickstarter project was canceled by the project creator on June 5, 2012.