I’ve always been fond of picture proofs — it was one of the things that drew me to graph theory, topology, and the logical graphs of C.S. Peirce and Spencer Brown in the first place. Sue was transitioning from Chemistry to Instructional Media when we first met and we often talked of crafting visual media for teaching mathematics from the ground up.
But the more I programmed the basal learning and reasoning modules the more I ran up against the limitations of the CSP–GSB calculi in their handed down forms and the limits of iconic representations in general. Changes had to be made. Curiously enough, many of the needed changes could be gleaned by looking more closely at the steps CSP and GSB used to arrive at their systems, by self-applying, iterating, and then taking those steps to the limit.