Zendo is an Icehouse game invented by Kory Heath, being the Icehouse equivalent of such logical deduction games as Mastermind and Eleusis. It is deeply inspired by Bongard Problems, those tricky deductive association puzzles made famous by Douglas Hofstadter, which are proving to be a provoking microdomain in cognitive science.

That aside, Zendo casts the players as a Master and eir Students. The play involves scrutiny of small, self-contained arrangements of Icehouse Pieces, termed Koans.

The Master, as an overseeing referee, invents a simple rule about the placement of Icehouse pieces within a Koan. Koans which comply to this rule are deemed to have the Buddha Nature. Some examples might be:

• A Koan has the Buddha Nature iff it contains at least one small red piece.
• A Koan has the Buddha Nature iff it contains a small piece stacked on a large piece.
• A Koan has the Buddha Nature unless it contains standing pieces
• A Koan has the Buddha Nature if the pip count of standing pieces is greater than 4.

-- but anything goes. Once the Master has decided upon a rule, e creates one Koan with the Buddha Nature and one without, marking them with a white and a black stone respectively. Once done, the bulk of the game begins. Players take turns to create probatory Koans, and get them marked. The goal is not to create Koans with the Buddha Nature, but rather to deduce the Master's Rule by examining its boundaries. Once a Student has formulated a wording of the rule the Master cannot disprove via the formation of a Koan, that student has acheived Satori (and, incidentally, wins the game.)

All in all, a fun addition to the Icehouse canon, and, as with most great games, a seemingly inevitable invention after the event. Recommended.