The (mafic?) object of 18 May brings us right back to JvN and prediction vs control. Depending upon how isotropic a skipping stone one picks, the resulting trajectory may be predictable or chaotic: in a world of too cheap-to-meter compute and effectors, one might imagine a "skipping stone" with LEDs and some kind of mechanical effectors that could be used to write Peristence-of-Vision messages by "skipping" it across a lake surface?