play-by-mail game
... that an observer once described a play-by-mail game as "the most complex game system on Earth"?
... that an observer once described a <b id="mwA7M"><a href="./Play-by-mail_game" id="mwA7Q" rel="mw:WikiLink" title="Play-by-mail game">play-by-mail game</a></b> as "the most complex game system on Earth"?