Zendo-like Induction Game for Playing Online

by Normal_Anomaly2 min read3rd Jan 201176 comments


Personal Blog

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.


76 comments, sorted by Highlighting new comments since Today at 2:06 PM
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I endorse moving the actual turn-taking mechanics onto another forum. I'm all for people having fun, but this mechanism generates an astonishing number of really really uninteresting comments in exchange, and I don't think the cost is worth it.

2Normal_Anomaly11yYeah, I noticed the state of the recent comments section myself. Sorry.

If you want to try playing regular expression Zendo against the computer, I have a JavaScript version here:


That way you can get immediate feedback.

As of this comment, I am going to sleep. I will be back tomorrow. Anyone in another time zone, carry on and I'll judge everything tomorrow.

On another note, I've been pleased with the response this has generated and am enjoying the game. I hope everyone else is too.

I love Zendo! I also don't want to hold up the turns, so I'd like to play and promise not to post more than one guess per round.

Mondo, 3, V cerqvpg lrf vf gur nafjre.

0Normal_Anomaly11yThis string is no. Benquo gets a guessing point.
0Normal_Anomaly11yWelcome! Your guess will be judged... sometime in the future. Before noon EST tomorrow. I'm moving your guess to the guess thread so they're all in the same place.
[-][anonymous]11y 0

I love Zendo! I also don't want to hold up the turns, so I'd like to play and promise not to post more than one guess per round.

Mondo, 3, yes.

Current turn list: Benquo, Larks, cata. Other people can still join.

ETA: Currently Larks's turn.

0cata11yI posted, but feel free to leave me out of the turn structure - I feel that having less turns isn't a big deal (at least, until a lot of data has been collected, and we're guessing the rule.)

Master 6 2 5 2

0Normal_Anomaly11yI don't know if you've seen the turn list yet. In case you haven't, it's your turn.
0Normal_Anomaly11yI want everyone to have easy access to all the previous guesses, so I'm moving this to the game subthread.

Meta stuff goes here.

3JoshuaZ11yOne issue with Zendo that doesn't necessarily make it a great game for actually improving rationality is that the rules are made by humans, so you can use psychology to get information. For example, I was playing with my family a few nights ago and my mother guessed a certain rule, my little brother immediately said "That's not Josh's rule. it isn't elegant." And sneakier players can do even worse stuff using sidechannel attacks. In particular, how long it takes for the Master to judge whether different configurations fit the rule can give a lot of information about the rule form.
2Normal_Anomaly11yUpvoted for truth. Hopefully this game will avoid those pitfalls because: 1) We've never met 2) The time it takes me to judge a rule is swamped by the time it takes me to notice somebody posted Also, using psychology to get information and improving your performance that way still requires rationality.
1anonym11yAren't those all just additional aspects of the game, additional constraints in the optimization process? If people will make inferences from how long the Master takes to judge whether different configurations fit the rule, then the Master should either systematically manipulate his times to give the wrong impression or introduce some random waits. And if you are known for only using elegant rules, then you're using a sub-optimal strategy for choosing the patterns, because you're giving away more information than necessary.
-2endoself11yHumans are the only things capable of reliably generating things that seem non-obvious to humans. The only reason the universe seems so good at it is because we pay less attention to the obvious things. I don't think we can improve on this issue easily enough for it to be useful for the purposes of the game.
2cata11ySince nobody else has done it, here's a post which I will keep edited with the current Master requests and responses: As of 03:29 Tuesday January 4 UTC: 6253 yes 21400 no 62533 yes 5142 no 60 no 6 no 6353 yes 824 no 6252 no 666 yes 6953 yes 65 no 01079 yes
0darius11yDoug Orleans told me once of a version like this he made to be played with an IRC or MUD bot (I forget which). A rule was a regular expression. (This came up when I mentioned doing it with Lisp s-expressions for the koans instead.)
0Normal_Anomaly11yRules clarifications: Mondo guesses may be changed at any time before the judgement is posted. If someone posts and it hasn't been judged yet, other people can feel free to post while you wait for me to show up.

Guess the rule here.

3cata11yI guess that you accept a sequence iff the sum of the digits in the sequence is greater than or equal to 16.
0Normal_Anomaly11yCorrect! You win the game. As a prize, you get +1 karma and it's your turn to be Master if you want another game. You might want to start another post, this one is crowded.
2Larks11yWow, I was miles off. I thought the rule was something like 'if it is of the form 6 X 5 3...' Also, time zones could make the mondo stages difficult; cata's guess was at 3:32 AM for me.
0Normal_Anomaly11yYeah, time zones were an unforseen difficulty. Perhaps for the next game, we could all agree on some time in advance and play in a chatroom.
0cata11yI'll pass on being master, since I can't really be on frequently and reliably enough to respond to guesses at a good pace. (I also like Normal_Anomaly's suggestion of just organizing a time to play in a chatroom.) If someone else stepped up, I would play again, though. This is a fun game! My other candidate rule was "if the last digit is divisible by 3," which almost works, except that 6 was not accepted (so it would have to have a special case.)
2endoself11y0 is divisible by 3.
0cata11yHmm, looking around, I guess it looks like you're right: Most people treat zero as evenly divisible by anything. I didn't know that before now.

Initial strings: “6 2 5 3” is yes, “2 1 4 0 0” is no.

0Normal_Anomaly11yMondo, 3, V cerqvpg lrf vf gur nafjre.
0Normal_Anomaly11yThis string is no. Benquo gets a guessing point.
0Benquo11yMondo 646
0Normal_Anomaly11yThis is yes. Cata and endoself get guessing points.
0cata11y0 1 0 7 9. Mondo.
0Normal_Anomaly11yThis comment has been up for an hour and a half and gotten responses from three of the five players, with one of the other two being a self-proclaimed occasional poster. Also I'm about to go to bed. So I'm going to judge it. It is a yes. Cata gets a guessing point for getting it right.
0endoself11yMaster 6 5 Don't add me to the turn structure. I'll post no more frequently then once per round, but I don't want to hold up the game.
0Normal_Anomaly11yNo. Thanks for the heads up.
0Larks11y6 9 5 3
0Normal_Anomaly11y[Assuming Master] Yes.
0Benquo11yMaster 666
0Normal_Anomaly11yReposted for cata: Master 6 2 5 2
0Larks11y8 2 4
0Larks11y6 3 5 3
0Normal_Anomaly11yMondo or Master?
0Larks11ySorry, Master for both
0Benquo11yMaster 6
0Normal_Anomaly11yNo. BTW, it is technically Larks' turn. If you don't feel like playing with a turn structure, though, you don't have to.
5Larks11yIt seems like things might flow a lot better without one - at the moment the game (like war) has both periods of excitement and periods of waiting for 8 hours, which together require a substantial re-organisation of one's day.
0Normal_Anomaly11yYeah, given how fast this is moving I'm thinking of shortening the time limit drastically. How about the first person to call Mondo on something suggests a time limit?
0cata11yI just called Mondo below. I would say that shortening would be appropriate, except that it would make it extremely hard for people in different time zones to play together fairly. (I'm in the US EST time zone.) If we opted out of shortening the Mondo time limit, I think we should lengthen the time limit on normal guesses to be commensurate, so that people can get into a rhythm. (An enforced delay on normal turns might also lead to more careful guesses, designed to obtain better information.)
0Normal_Anomaly11yI don't think it should take more than 5 minutes to come up with a valuable guess, and given that people leave their computers sometimes, an enforced delay would likely be an annoyance. I'm in the US EST time zone too. If anybody here isn't, let me know. I'll judge your Mondo guess tomorrow, unless it gets several replies before I leave. Edit: judged it.
0cata11yI made my first guess! Unfortunately, with the way the times worked out, there are outstanding Mondo requests. Since I would win the game if my guess is confirmed, I will purposefully answer the Mondo requests as if it were denied. Normally, I assume that (if we were being careful with the order) I would hear the result of my guess before other players continued.
2Benquo11yWhoops - I guess I am unclear on the turn structure, as there is not a well defined # of players; but I will wait until Larks catches up, and yield a free turn to Larks by way of apology.
0Normal_Anomaly11yThat's courteous of you; thanks. I was just going to let people join and enter the turn list at whatever point it was at when they entered. So far it's just you and Larks. I'm going to reply to his comment in case he doesn't know it's his turn.
0Benquo11yMaster 6 0
0Larks11yMaster 5 1 4 2
0Normal_Anomaly11yIn case the turn structure is unclear, it is your turn. You get two turns this time, because you were skipped earlier.
0Benquo11yMaster 6 2 5 3 3