Kory Heath Designs

Does a dog have Buddha-nature?
This is the most serious question of all.
If you answer yes or no
You lose your own Buddha-nature.

Zendo is a game of inductive logic in which the Master creates a rule and the Students attempt to discover it by building and studying arrangements of plastic pyramid-shaped pieces (known as “Icehouse pieces”). The first student to state the rule correctly wins.

Looney Labs published a commercial version of Zendo, but it’s currently out-of-print. You can still purchase Icehouse pieces from Looney Labs in the form of Treehouse sets.

What You Need

• A number of identical Treehouse sets. (The more the better. Four is about the minimum.)
• A fair number of black and white stones.
• A fair number of stones of a third color.

Setup

Choose someone to be the Master. The other players are the Students. Give each Student a black and a white stone, to serve as “answering stones”. The remaining black and white stones are “marking stones”, and the stones of the third color are “guessing stones”. Put all of the marking stones and guessing stones in front of the Master, and put all of the pyramids into a global stash within reach of all the Students.

The Master must choose a rule, create two initial koans, and pick someone to go first.

Koans

Over the course of the game, players will create different arrangements of one or more pyramids on the table. Each arrangement is referred to as a “koan”, pronounced “KO-ahn”. Koans can be set up in any fashion, as long as they don’t touch other objects or other koans.

Choosing a Rule

When you are selected to be the Master, your first task is to devise a secret rule that will be used during this game of Zendo. For your first several games, you may want to use one of the rules listed on the Rules For Beginners page. These are good rules for new players. See the Terminology page for any terms on this page that are not clear. When the players are more experienced, you can invent your own rule.

According to your rule, some koans will “have the Buddha-nature”, and others will not. For the Students, the object of the game is to try to figure out what your secret rule is. As the Master, your job is to act as facilitator; you are not actually a player, and you are not in competition with any of the players.

Examples

• A Simple Rule: A koan has the Buddha-nature if and only if it contains one or more green pieces.
• A Very Difficult Rule: A koan has the Buddha-nature if and only if it contains an odd number of pieces pointing at other pieces.
• A “Negative” Rule: A koan does not have the Buddha-nature if it contains exactly three pieces touching the table; otherwise it does.

Initial Koans

As the Master, start the game off by building two koans in the middle of the playing field. One should have the Buddha-nature according to your rule; place a white stone next to it. The other should not; place a black stone next to it. You will be marking all of the koans in this way throughout the game. Starting koans need not be complicated, even with experienced players.

Turn Order for Students

1. Build a Koan

• Create a new koan using one or more pyramids from the global stash.

2. Say “Master” or “Mondo”

• Master: The Master will immediately mark the new koan with a black or white stone.
• Mondo: All Students must guess if the new koan has the Buddha-nature or not. Pick up your own answering stones and hide your answer (black or white) in one fist. Hold that fist out over the playing field, and wait for all of the other Students to do the same. When everyone is ready, reveal your guess. The Master will mark the koan with the correct answer, and will award a guessing stone to each player who answered the Mondo correctly.

3. Guess the Rule (optional)

• Make a Guess: If you have any guessing stones, you may choose to spend one or more of them to try to guess the Master’s rule. Give a guessing stone to the Master and then state your guess as clearly as you can.
• Clarify the Guess: If the Master does not fully understand your guess, or if it is ambiguous in some way, the Master will ask clarifying questions until the uncertainty has been resolved. Your guess is not considered to be official until both you and the Master agree that it is official. At any time before that, you may retract your guess and take back your stone, or you may change your guess. If any koan on the table contradicts your guess, the Master should point this out, and you may take back your stone or change your guess. It is the Master’s responsibility to make certain that a guess is unambiguous and is not contradicted by an existing koan; all Students are encouraged to participate in this process.
• Master Disproves Guess: After you and the Master agree upon an official guess, the Master will disprove it, if possible. The Master builds a koan which has the Buddha-nature but which your guess says does not, or builds a koan which does not have the Buddha-nature but which your guess says does.
• Repeat: Once the Master has built a counter-example and marked it appropriately, you may spend another guessing stone, if you have one, to take another guess. You may spend as many of your guessing stones as you wish during this portion of your turn. When you are finished, the action passes to the Student on your left.

Winning

If the Master is unable to disprove your official guess, you’ve achieved enlightenment—you’ve discovered the Master’s secret rule and have won the game!

Further Reading

• Details and Clarifications
• Terminology
• Rules For Beginners
• Tips for the Master
• Tips for the Student
• Design History
• Zen Glossary

Acknowledgments

• Game Design – Kory Heath
• Game Development – John Cooper, Kristin Matherly, Jacob Davenport
• Playtesting – Peter Hammond, Andy Looney, Kristin Looney, Alison Frane, Gina Mai Denn, David Bender, Michelle Lepovic, Eric Zuckerman, Beth Zuckerman, Mike Sugarbaker, Ryan McGuire, Dan Isaac

Links

• A Review by Tom Vasel
• A Review by Bruno Faidutti
• Zendo won the 2003 Origins Award for “Abstract Board Game”.
• Zendo was named one of the 2005 Mensa Select games by Mensa.
• Zendo was published in Playing with Pyramids.
• Funagain Games still sells the Zendo Cards that came in the commercial version of the game.
• If you like Zendo, you’ll love Bongard Problems. You can find hundreds of them at Harry Foundalis’s Bongard pages. (Check out the index link.)
• Eleusis is a famous induction game designed by Robert Abbott. Check out his Eleusis pages. Also, don’t miss his great Logic Mazes website.
• Stanley Anderson’s game Jewels in the Sand was an important influence during the early design of Zendo.
• Karl von Laudermann has created The Zendomizer, a Java applet that randomly generates Zendo rules. Also available for handheld devices.
• William Shlaer has created Zendo-san, a windows program that plays a somewhat restricted version of Zendo.
• Drunken Master (Zendo the Drinking Game)
• Zendo at BoardGameGeek