Description

Slide with a promotional image of the Invisiclues booklets for Planetfall and Infidel. The image shows one cope of each booklet closed, and one copy of each booklet open with a decoder pen on each open booklet.

InvisiClues were hint booklets sold through Infocom’s Zork Users’ Group. They were small booklets with a series of questions related to the game that was the subject of the book. Highlighting blank boxes under the questions with a specialized decoder pen revealed hints that would allow players to solve puzzles in the game itself.