Making "Rodoku"

As many of you know, the Rosenstock Doughty household often refers to itself in shorthand as the RoDos. Sometime last year, while thinking of ideas for New Years' cards, the idea of changing Sudoku into "Rodoku" popped into my head. I thought it would sound funny. I didn't exactly know how I'd use that, but just as I was getting ready to start thinking about it, Jeremy came up with his excellent suggestion for a card based on a GPS.

I finally returned to it this year. I figured I'd have a great head start, since the basic idea was already set. But it turned out that there were a number of challenges that still had to be overcome, not the least of which was actually coming up with a reasonable cover that would illustrate the concept.