After finally getting digits 0-7 to display, kid wanted to see the digits count. So, a bit more coding with NAND gates--implementing increment directly from a truth table. Finally, "lucky for you kid, I just happen to have a quad-input flip-flop and a 555 timer (as one does)."
So we finally ended up with this beautiful rat's nest of work, slowly counting digits.
Thus concluding the first lesson on "how do computers work?"
deshipu
juandesant