In a state of drowsiness yesterday, I began to think of yo-yos, and how yo-yo playing is a constrained universe of expression. Expression of creativity. It’s a space in which to invent new tricks. It even has a vocabulary; see the description of the trick “Barrel Rolls” (emphasis mine):
Begin with a bottom mount. Insert your right index finger between the doubled strings and perform an underpass with your left hand. Rotate both hands until you are back in the bottom mount. The underpass and hand rotation must be one smooth, continuous movement or the yo-yo might snag. Once you are back in the bottom mount you can either do more Barrel Rolls or drop all the strings and call the yo-yo back to your hand. This trick can be done from a Trapeze or a split bottom entry as well.
Humans seem to have a tendency to invent constrained universes of expression. I also thought about Go, but now I’ve got to go (sorry). I wonder whether this is discussed in Homo Ludens: A Study of the Play Element in Culture by Johan Huizinga.