The decoder pen, yes-no pen, yes-know pen or magic pen book is a combination of decoder pen or
marker specially designed to reveal
invisible ink
Invisible ink, also known as security ink or sympathetic ink, is a substance used for writing, which is invisible either on application or soon thereafter, and can later be made visible by some means, such as heat or ultraviolet light. Invisible ...
-encoded pictures or writing,
in the form of answers to questions or hidden parts of pictures, with specially created
children's books
A child ( : children) is a human being between the stages of birth and puberty, or between the developmental period of infancy and puberty. The legal definition of ''child'' generally refers to a minor, otherwise known as a person younge ...
with hidden words and pictures. They were most popular in the 1970s, but continue to be sold at gift shops. Often they were in the form of trivia games, which enabled the player to guess before revealing the answer. Brands of books for use with decoder pens include Yes & Know, and surprise Ink.
However, the pen and paper can be damaged easily if excessive rubbing is used. Therefore, most invisible ink books contain an advisory saying to use a very gentle back and forth motion - not a circular grinding motion, when using the books.
Fans of the adventure games released by
Sierra Entertainment
Sierra Entertainment, Inc. (formerly On-Line Systems and Sierra On-Line, Inc.) was an American video game developer and publisher founded in 1979 by Ken and Roberta Williams. The company is known for pioneering the graphic adventure game genre ...
in the 1980s such as ''
King's Quest
''King's Quest'' is a graphic adventure game series, released between 1980 and 2016 and created by the American software company Sierra Entertainment. It is widely considered a classic series from the golden era of adventure games. Following th ...
'' and ''
Space Quest
''Space Quest'' is a series of six comic science fiction adventure games released between 1986 and 1995. The games follow the adventures of a hopeless janitor named Roger Wilco, who campaigns through the galaxy for "truth, justice and really cl ...
'' are also familiar with the decoder pen, which was used to reveal the answers to hints in the hints book sold for each game. Eventually these were replaced by a colored translucent plastic window, which eliminated a visually interfering red pattern.
Infocom sold similar hint books called "
Invisiclues
InvisiClues were hint booklets sold by Infocom to help players solve puzzles in their interactive fiction computer games. " for their
interactive fiction games.
References
External links
Lee Publications(publisher of invisible ink books)
Note: there is a warning about theft of information when accessing this link 26/11/2021.
Writing implements
Art and craft toys
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