Lexicon is a game played on Waterpoint that is sort of like Zendo or Mastermind, but played with words.
The help from Lexicon is reproduced below, because the last time I (rlpowell) played Lojban Lexicon was 8 months ago and I don't remember the details.
At the first LogFest@PhilCon (in 2005), we played a variant that worked with Lojban sentences, which I will try to describe here, as I say, from memory. This page will become less tentative as the rules become clearer.
HELP ON THE LEXICON GAME FEATURE
================================
This is the Feature Object interface to version 2 of the game of Lexicon.
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The game of Lexicon is a guessing game based on Eleusis (http://www.netaxs.com/people/nerp/eleusis0.html) and Zendo
(http://www.wunderland.com/WTS/Kory/Games/Zendo/).
One person, the god, invents a lexicon. A lexicon is a set of words. The set may be infinite, but there must be a finite rule
that decides whether a word is in the lexicon or not. The set must be fixed at the time the rule is chosen (i.e. the rule can't
involve the outcome of some future event). A word is any string of characters-- it does not have to be an English word! (Of
course, god can make that part of the rule.) For example, the rule "starts with a 'b'" determines a lexicon that includes the
words "black", "butter", and "baz", but does not include the words "white", "cob", and "foo".
After god has set a rule for the lexicon, players may test words, and god passes judgement on whether the tested words are in the
lexicon or not. There is no turn-taking; players may make tests whenever they like, but may only have up to 3 unjudged words at
any time.
Players may think they've figured out what the rule is, and make a guess. If the guess is correct, god declares the guesser to be
the winner, who becomes the new god. (Note that the guess does not have to match the rule statement exactly; they just must
determine exactly the same lexicon.) If the guess is incorrect, god must provide a counterexample: a word that is either in the
lexicon but violates the guessed rule, or NOT in the lexicon and satisfies the rule. If there is no counterexample in the list of
words already judged, god must judge a new word that is a counterexample.
With Lexicon v2, it is possible (and expected) for the god to provide both positive and negative counterexamples, or declare that
there is no such counterexample.
The 'ENABLE' word list, which has often been referred to in Lexicon rules, can be found at:
http://personal.riverusers.com/~thegrendel/software.html
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Original implementation by Ragnar. Current implementation by Marn.
@lexicon-o*ptions @lex-o*ptions @lexo*ptions
============================================
Set options regarding Lexicon.
@guess
======
Usage: @guess <what you think the rule is>
@retract-guess @r-guess @unguess @retract-rule @r-rule @unrule
==============================================================
Usage: @retract-guess [<guess-number>]
Retract a rule guess, thereby declaring that the god need not find a counterexample to it. The guess number is optional if you
only have one.
@rule*s @guesses
================
Usage: @rules
@rules [retracted] all|<number>
With no argument, displays active rule guesses.
With an argument, displays all or the last <number> rule guesses, including those with counterexamples.
Also displays your rule, if you are god.
@lex*icon
=========
Usage: @lexicon
Displays judged words, hints, and partially correct guesses.
@lexlist @lexw*ords
===================
Usage: @lexwords [with*-names] [chron*ological] [<judgement-type> ...|all] [/<pattern>/]
Display judged words.
o 'with-names': displays who tested each word.
o 'chronological': displays words in the order they were tested.
o If no judgement types are specified, defaults to showing only "yes" and "no".
o '/pattern/': displays only matching words (see `help regular-expressions'[1])
@lexs*tatus
===========
Displays current tests and guesses. If you are not god, displays who is.
@test*s @test1 @testn
=====================
Usage: @test <word> <word> ... (if @lexoption -testphrase)
@testn <word> <word> ...
@test <word or phrase> (if @lexoption +testphrase)
@test1 <word or phrase>
@tests
Test whether the words are in the lexicon, or, with no arguments, see all current tests.
@retract-test @r-test @untest @retract-test1 @r-test1 @untest1 @retract-testn @r-testn @untestn
===============================================================================================
Usage: @retract-test <word> ... (same variants as @test)
Retract a test, thereby declaring that the god need not judge it.
@hint*s
=======
Usage: @hints Displays all hints.
@hint <text> Provide a hint (if you are god).
@retract-hint @r-hint @unhint
=============================
Usage: @retract-hint <num>
Remove a hint.
@set-rule @setrule
==================
Usage: @set-rule <rule>
Set the rule.
@amend-rule @append-rule
========================
Usage: @amend-rule <text>
Adds further text to the rule. You cannot remove it or change the original rule. Use with care.
@set-test-limit
===============
Sets the number of simultaneous unjudged tests players may have.
@jy @jn @judge-*
================
Usage: @judge-yes/@judge-no/@jy/@jn <word1> <word2> ...
Judge that the given words are all in/not in the lexicon.
@program-judge @autojudge-program @autojudge-code
=================================================
Usage: @program-judge [batch] [<code>]
Specify code to automatically judge words. As with the eval command, the code must be a single expression or start with ";" and
contain a 'return' statement.
With no argument, displays the current code.
The word to judge will be in the variable "word". The code should return its judgement (e.g. "yes" or "no"), or a non-string to
make no judgement.
If 'batch' is specified, a list of words will be placed in the variable "words" and the code will be expected to return a list.
The code will be run with the permissions of $nobody.
@reautoj*udge @rej*udge @autoj*udge
===================================
Usage: @reautojudge [<words>]
Force the specified words to be autojudged. Rejudges all words if none are given.
@counter*example @ce
====================
Usage: @counterexample <guess-num> with <words>
Provide <words> as counterexamples to the rule guess. You must judge the words before you can use them as counterexamples.
@retract-counter*example @r-ce @uncounter*example @unce @retract-ce
===================================================================
Usage: @retract-counterexample <guess-num> with <word>
Retract <word> as a counterexample for the rule guess.
@noce @nocounter*example @no-ce
===============================
Usage: @nocounterexample <guess-num> with <judgement>
Declare that there are no counterexamples of type <judgement> for the specified <guess-num>.
This declaration refers to the complete lexicon, not the subset of tested words. If there is a possible counterexample but it has
not been judged, you should judge it and use @counterexample.
To retract an incorrect @noce, provide a counterexample.
@winner @deify
==============
Usage: @winner <guess-num>
Declares the specified guess to be correct, and therefore the player who entered it to be the winner.
@lexabort @lex-abort
====================
Usage: @lex-abort
For use only in extreme circumstances. Ends the current game and starts a new one with no god.
@abdicate
=========
Usage: @abdicate to <player>
Make <player> be the new god. You can't do this once words have been judged.
An accidental "feature": if you set a bad rule, you can abdicate to yourself to enter a new one.
Usage: @abdicate
Allow anyone to become god (by entering a rule).
@lexform @lex-form
==================
Open a TWin form which provides an alternate interface for playing Lexicon.
@lexicon-his*tory @lex-his*tory @lexhis*tory
============================================
Usage: @lexicon-history - number of games
@lexicon-history <game #> - details of game
@lexicon-history <game #>..<game #> - range of rules
@lexicon-history /regex/ - searches rule text
@lexicon-history ~player - game gods
<game #> may be $ (last game) or $-<num> (<num> before last game)
@lexicon-scores @lexscore*s @lexgods @lexwinners
================================================
Lists those who have been gods of past games.
o Players shown (like this) have set the +mute option.
o Players shown ((like this)) have removed the feature.
@lexwho @who-lex*icon @lexplayers
=================================
Usage: @lexwho [all]
Like @who, but only those who have the Lexicon feature.
lsay lem*ote l:* lthink lthikn l%*
==================================
Usage: lsay <text>
Talk with other Lexicon players.