Card games belonging to the Eights group have been popular with schoolchildren and college students at least since the 1960's. Part of their attraction is the ease with which increasingly elaborate rules can be added; success in these games depends largely on the ability to remember the rules and act on them correctly within a limited time.
Mao is a recent addition to the group, which is especially popular in the USA. The main feature of Mao which distinguishes it from many of its predecessors is that there is a rule against explaining or asking about the rules. New players are expected to join a game and deduce the rules of play by observation, trial and error.
This ban on explaining the rules makes it rather awkward to produce a useful web page about Mao without violating its key principle, but that has not stopped several people from trying.
- Ka Wai Tam's Mao page [archive copy] uses an interesting approach. You are given a description of a sample game, and from this you have to deduce the rules for yourself - as in real life.
- Glenn Overby's page Mao: A Sample Game [archive copy] adopts a similar method to demonstrate the "Motor City Variant".
Nicholas Cheung's page on Mao (archive copy) may also help to give you a flavour of the game.
Although many people have the impression that the game is named after the Chinese leader Mao Zedong, it seems likely that the direct ancestor of Mao is the German game Mau-Mau, which works on somewhat similar principles. Another theory links it to the following passage from Arthur Machen's short story The White People, in which a young girl recording her bizarre experiences with witchcraft:
"I must not write down the real names of the days and months which I found out a year ago, nor the way to make the Aklo letters, or the Chian language, or the great beautiful Circles, nor the Mao Games, nor the chief songs."
This story was written at the end of the 19th century, which must be several decades before the card game Mao was invented. However it is conceivable that whoever named the card game had read and was influenced by the story.
A small collection of Mao Variations can be found in the Invented Games section.