Zendo

Zendo requires a set of Looney Pyramids (formerly called Icehouse Pieces) in multiple colors and sizes, along with marking stones or tokens to indicate which structures follow the master's secret rule. The full rules are available for free from the Looney Labs website, so if you already own pyramids, you can play without additional purchases.

One player—the master—creates a hidden rule that determines whether a pyramid structure 'has the Buddha-nature,' such as 'must contain exactly one blue piece' or 'must have a large piece on top.' The master builds two example structures, one that follows the rule and one that does not, then other players build their own structures and receive feedback to inductively deduce the rule.

Zendo's mechanics are simple to explain—build structures and get yes-or-no feedback—but the deductive challenge can scale dramatically with the complexity of the master's rule. Most newcomers grasp the concept quickly, though a master who picks an overly obscure rule can frustrate new players.

Zendo plays well with 3 to 5 participants total, with one person acting as the master and the rest as students trying to crack the rule. With larger groups, turns can drag as each player builds and guesses sequentially, so many groups prefer to keep it to about 4 players.