Watching Layer Tennis last Friday, commentator John Gruber compared the competition to Calvinball, which brought me back to my childhood, reading the Sunday funnies. Remember Calvinball? In my book, it’s the ultimate Nomic game — a game in which the rules change and evolve as part of gameplay.

Back in April, I wrote about another Nomic game, 1000 Blank White Cards. 1KBWC (as it’s, uh, less commonly known) is a card game in which players make up their own cards, which may implement new rules (like “you must hold 40 cards in order to win” or the less-fun “holder of THIS CARD wins”). Calvinball is similar, but a bit more active — it is classically played outdoors — and more devious: according to the official rules, section 1.2, new rules may be declared either audibly or silently. The other major difference is that Calvinball involves a ball (which, according to section 2.2, “may be a soccerball, volleyball, or any other reasonable or unreasonable, spherical or non-spherical object”).

I think I’m a Calvinball fan because it’s a game of wit, rather than one of physical prowess. (Also you get to wear a mask, and that sounds pretty fun.) I certainly had my share of childhood games which devolved into arguments over who shot whom, but of course we also displayed this Calvin-like behavior of devising new rules. That’s what kids do. (I recall one particularly egregious example: during a Monopoly game I once declared, “I’m allowed to take $500 bills because I’m the banker. That’s what banks do, they have lots of money.”)

Prospective Calvinball players should consult the official rules, read the Wikipedia sub-entry on Calvinball (which is admirably full of citations), or learn more about Nomic.