Zendo is a game of inductive logic by Kory Heath where one player – the “master” – creates a secret rule and the other players – the students – propose new “koans” and make guesses in order to discover the master's rule (“become enlightened”).
In the original game of Zendo, koans are configurations of stackable pyramids that come in several sizes and colors. These pieces are known as Looney Pyramids or Icehouse pieces.
Zendo need not use pyramids exclusively. Another popular variant is Text Zendo, where koans are comprised of words instead of pyramids. Text Zendo is the default format for Zendo challenges on SDG. Number Zendo and Image Zendo are available as variants. Using just these three “mediums” for Zendo, quite a few variations have been invented and used by SDG players.
The same basic rules as the Icehouse Zendo game are used for nearly all Zendo variants, so refer to the link above to learn the game. Guidelines and notes specific to each variation are given below.
Image Zendo on SDG is usually used for pyramid Zendo, but any images may be used. The master will tell you what makes a koan allowable in the dojo. Note that SDG resizes all images to 200×200 pixels as this may place limitations on what is possible to represent.
Pyramid Zendo is played either with photographs of actual pyramids or with 3-D images of pyramids rendered with the POV-Ray 3-D raytracing program. See a sample game.
SDG maintains a searchable library of pyramid koan images with more than 100,000 entries! You will often be able to find the koan that you need already in the library. If you do need to create a new koan, use the SDG POV-Ray Playground. The following resources are all accessible from the Services link on the main SDG site:
Pixel Zendo is a recent variation invented by SDG user mathgrant and uses images of rectangular grids of colored squares or “pixels”. In the games played so far, allowable koans have been of any size (as long as the grid is rectangular) and pixels are usually only black or white with some other color (typically red) used to separate the pixels. There is no reason though that a master could not choose to limit the size or allow additional pixel colors for a particular game. See a sample game.
See the page on Making Pixel Koans for software suggestions, tips, and templates that make it easy to create Pixel Zendo koans.
The following terminology has been suggested by mathgrant and adopted by other players of Pixel Zendo.
SDG user Analog Kid has suggested that images composed of lines, circles, squares, or any other 2-D shapes in various colors and sizes would be a viable alternative to the 3-D pyramid images for playing Zendo on SDG. No one has yet tried running such a game.
Text Zendo is typically played with koans being either a single word, a sequence of words, or arbitrary text. But a huge number of specialized variations are possible within Text Zendo and some masters have experimented quite liberally. A few possible variations that have been used are given after the basic rules for “Word Zendo”.
SDG user Zotmeister has invented a variant where koans are combinations of standard playing cards. Cards are represented in the dojo by letters corresponding to their rank (AKQJT98765432) followed by their suit (SHDC). In one game, koans were ordered pairs of cards written “X on Y” (eg. “2H on 2C”). In another game, koans were unordered sets of four distinct cards (eg. 2C, 5C, 8D, JD). Many other koan formats for Playing Card Zendo are possible and, indeed, this variant suggests that Text Zendo on SDG can be used to play Zendo with any sort of collection of real or imagined objects, as long as a clear notation for the koans can be articulated. (see Musical Zendo below).
In Meta Zendo (invented by SDG user GregF ?), koans are Zendo rules for one of the other types of Zendo and the Master's rule is a “metarule” that describes which Zendo rules have the Buddha nature. If that sounds convoluted, consider these examples from a sample game here on SDG in which koans were valid rules for single-word Text Zendo.
The Master's metarule was AKHTBN iff it would mark “zendo” white.
HAS koans included:
HAS NOT koans included:
To get a better sense of the possibilities for Meta Zendo, see the rule and the discussion in another sample game.
In Cypher Zendo, the Master chooses a simple substitution cypher (a “secret code”) that replaces each letter of the alphabet by another particular letter such that no two letters are replaced by the same letter. Koans are strings of letters and they have the Buddha nature iff the cypher transforms them into a valid word. Students are trying to guess the master's cypher (i.e. break the secret code). The Master and students use an online dictionary as a reference for which words are considered valid. For complete rules and examples, see the Cypher Zendo page. See a sample game.
SDG user AnalogKid thinks that using musical melodies or chords as koans could be fun. Koans could be represented on SDG using a textual notation indicating pitch and rhythm (something like “4/4 - 4: C4 C4 G4 G4 | A4 A4 2: G4 | 4: F4 F4 E4 E4 | D4 D4 2: C4” for Twinkle, Twinkle, Little Star). Many different properties could be used to form rules: pitches, intervals, scales, key, durations, meter, etc.
In Number Zendo, koans are usually a single number. Many Number Zendo dojos use only integers, and often only positive integers. Some have used “decimals” (real numbers with a terminating decimal representation), ANY real number (including repeating fractions or irrational numbers), complex numbers, or pairs of numbers (planar coordinates). SDG user Jesse even ran a game where koans were single-variable functions! (albeit in a Text Zendo dojo). The Master will tell you what makes a valid koan.
Rules might consider
In other words, some require math, others won't.
Here are some examples of things to consider when playing Number Zendo:
Text Zendo is the default format for Zendo challenges on SDG. Number Zendo and Image Zendo are available as variants.