Actually, what we've come up with is an ubercard game, named Calvincard. The rules are simple: you take a deck of cards, and after that you make up rules as you go along. A new rule can elaborate on an old one, but not contradict it flat-out, like the blessings of fairy godmothers.
You can start out taking turns making new rules, but even that will probably change as the game progresses. You keep going until you are either satisfied with the game, or it has broken out into fisticuffs.
The resulting game this week was rather fun, but I cannot yet report on it because DOB's last rule about scoring grew so complex my brain went on overload and I had to go take a nap. As fun or more fun than playing the game, however, was calculating out the probability of all the different hands to determine how they should be ranked.
OK, maybe we are hopeless nerds.
And on that note, here's a fun little puzzle:
The ants go marching one by one, two by two, all the way up to ten by ten. But the little one is always left out by himself. What's the smallest number of ants that could do this? Bonus points for a particularly simple process to find out.