When I was growing up, one game that fascinated (and still fascinates) me is opon ayo (more commonly known as oware). I noted how placing a single extra seed in a hollow could change the total number of seeds in the hollow; this in turn could change the the effect of playing out the seeds in that hollow, which in turn could change the number of seeds in other hollows, which ultimately could change the way the entire game was played out.

Of course, this phenomenon isn't limited to...