The virtues of Infocom text-based adventure games have been expounded upon in great detail; many people are familiar with them either through first-hand experience or reading the websites, nodes, and magazine articles. For years, players have pondered the complicated (and sometimes witty) puzzles contained in these creative games.

InvisiClues were Infocom's response to people who thought the games were too hard.

An exercise in steganography, InvisiClues books would be purchased at the same stores that sold the games. While in contemporary times, we have "Prima's Official Strategy Guides" that give away every secret in the game with full-color glossy pages, the InvisiClues booklets were much more subtle -- and more economically printed.

Each book was filled with questions that may be asked by players as they proceeded through the games. Below each question was an empty box. Players would use a special pen that accompanied the game to highlight the box, line by line. Hints written in invisible ink regarding the question would magically appear. Typically, each question would have several responses, and players would only reveal answers until they had the degree of hint they were looking for. This avoided spoiling the game by providing a walkthrough but speeded things up by pointing the player in the right direction.

So that a player couldn't read through the questions and ruin his or her entire game, distractor questions were scattered throughout. Someone couldn't be sure whether the question about a grue was legitimate or not -- until they were face-to-face with the monster later in the game.

Most of the InvisiClues booklets ended with a list of all the points possible in the given game (hidden, of course) and a list of "fun things to try" that would activate entertaining (and sometimes deadly) descriptions of the player's environment.

The bulk of the InvisiClues library are available on the later Infocom game collection CD-ROMs in PDF format and online in various stages of hidden-ness.

Sample InvisiClues question with all answers, from InvisiClues for Enchanter:

Why did the dragon wear red sneakers?

1. Search the laundry room.
2. NITFOL the dragon and ask him.
3. Because his blue ones were in the wash.

Sometimes the best entertainment value in the book was to develop the answers to the distractor questions, as these had some of the longest answer sets available.

NB: Some InvisiClues packages also included pre-drawn maps for the game. These usually added significant amounts of flavor to the Infocom experience, as they were designed in the same style as the value-added material in the original game box.