In Zendo, the secret rule is the rule, known only to the master, that determines which koans have the Buddha nature and which don't. Every student seeks to discover this secret rule. Secret rules are invalid if they violate the Spock rule or the Protractor rule.
Example secret rules
These are roughly in order from easiest to toughest.
- AKHTBN if it has at least one blue pyramid.
- AKHTBN if it has exactly one weird piece.
- AKHTBN if it has two pieces with base corners touching.
- AKHTBN if it has at most one large pyramid.
- AKHTBN if it has exactly three pyramids.
- AKHTBN if it has no more than one piece of the same color.
- AKHTBN if it has at least one green piece, but no blue pieces.
- AKHTBN unless a red pyramid touches the table.
- AKHTBN if every pyramid is touching a number of pyramids equal to its pip count.
- AKHTBN if no medium pyramids point at yellow pyramids.
Karl von Laudermann has created The Zendomizer, a Java applet that randomly generates Zendo rules. Also available for handheld devices. Find it at http://www.doodpants.org/karlvonl/Zendomizer.html