>That's the way we do it here too, but then I'm a math person - and do those "Cross Sums" puzzles daily. The MB sums are neat little puzzles to solve :)

I would agree that the MB sums are easier to use, especially when you've got 'em memorized. But they aren't very readable to someone who doesn't work that way. BTW I share your interest in puzzles, etc., and I have no problem with this approach from that POV. We all love tricks and shortcuts, but sometimes readability takes a hit.