Mao belongs to a class of games called inductive reasoning games. They're mostly crap, but there are a few gems. IMO the best one of the bunch is Zendo where one player makes up a rule that determines whether a grouping of playing pieces is valid or not (usually played with Treehouse pieces, but e.g. a limited selection of lego pieces can also work). The other players then basically need to use an experimentation / induction loop to determine the rule. This can be really fun in a hackerly group. And once the players get experience, it's surprising how complicated rules are solveable.
Zendo is great - I played it again with my nine year old godson last weekend when he was here having a sleep over.
Tangentially: this kid is an awesome proto-nerd, and I fully expect that he'll be posting at HN in another 6 to 8 years - for the last two years he's wanted to program a computer game, and I told him that he and I would learn HTML5 and JS together when he turns 10. We've already got the domain name picked out.
If you haven't engaged with an intellectually precocious kid, you can't imagine how fun and rewarding it is.
The story of the Zendo design process is a great read: http://www.koryheath.com/games/zendo/design-history/