Thanks to the BGA dev community for all the resources and for answering my questions when I was doing something stupid. I also owe credit in particular to the code of W. Michael Shirk's Grosstarock implementation and Drasill's Coinche which were both very useful to stare at when I was trying to understand the framework.
Additionally I have taken inspiration from the implementation of several great games available on BGA - in particular in addition to the above, Hungarian Tarokk, Solo Whist, and Phat. Go play them, they are excellent!
The banner image is a modified version of this Harris and Ewing photograph of card players from the USA Library of Congress. The game they are playing is certainly not Calypso (being seemingly three players, and dating from 1936, nearly twenty years before Calypso's conception), but might pass for it if you squint pretty heavily.