Yesterday I published a new Plankton Valhalla essay titled Recursion, Tidy Stars, and Water Lilies, and it marks a little milestone for me. Where AeMug blog posts are frequent, regular, and a bit random, PV essays come "when they're ready", and they tend to be longer (this latest one might be a record, at almost seven thousand words!). I set out with the idea to write a single essay explaining cybernetician Stafford Beer's awesome maxim, the purpose of a system is what it does (POSIWID for short).