I recently encountered the inductive logic game Zendo ¹, and it looks like a great game for aspiring rationalists. I’d like to play a game like it among the people on this forum. However, Zendo is very visual, with an emphasis on color and position of pieces, so it would be difficult to play over the Internet. So I’ve adapted the concept and rules of Zendo to a format that can be played in an LW thread.

The basic premise of Zendo is that of trying to figure out a rule by observing which entities do or do not comply with it. One player, the “Master,” devises a rule and presents one structure that does and one that does not comply. In the online version, these are strings of 1-digit numbers. For instance, the rule might be “at least 2 of the digits are odd.” Then “2 5 1 0 ” would satisfy the rule, and “8 3 2” would not. The rule can be any level of complexity and may concern anything about the numbers, like “The string must contain at least 4 digits” or “The sum of the first two digits must be greater than the sum of the last two” or whatever. It may not concern anything other than the string, such as the timestamp of the post.

Players take turns by proposing a string in reply to the comment with the first two strings, and saying either “Master” or “Mondo”. If the player says “Master,” the Master will reply to the comment containing the string and say “yes” if it complies with the rule and “no” if it does not. If the player says “Mondo,” all players have some amount of time to post a reply guessing whether or not the string will meet the rule before the Master judges it. Currently this time is 8 hours so everyone will have time to see it, but if this seems too long it can be shortened. Traditionally this is done by concealing a colored stone in one’s hand with nobody seeing anybody else’s guess until time is up, so if you want post your guess in rot13 surrounded by gobbledygook (e.g. fyqxwsfyxqwstfyxlrffyqxwsyfqxwtsfy). Please don’t read other people’s rot13. At the end of the time period, the Master will judge the string and give everyone who guessed correctly a guessing point.

At the end of your turn, after your string has been judged, you may spend one guessing point to reply to the “Guess the rule here.” comment and guess the rule. The Master may ask clarifying questions about ambiguities in the guess. When the Master is satisfied that e understands the guess, e will either pronounce the guesser the winner or provide a string satisfying the guess but not the true rule or vice versa. The guesser may guess until e wins or runs out of guessing points.

I’ve decided an initial rule, and started a game in the comments. To join the game, reply to the comment containing the first two strings. To comment on the merits or problems of the game, say that this shouldn’t have been posted, ask questions, or suggest changes to the rules, reply to “Meta stuff goes here.”

1: The link is broken. It's supposed to go to http://en.wikipedia.org/wiki/Zendo_%28game%29 .

EDIT: The first game was fun, but time differences made it a bit chaotic. The second game will be attempted on IRC chat. To join, suggest a time, or volunteer to be Master, post a comment to that effect.