** How does it work?**

Well, whenever you take the sum of a two digit number away from that number (i.e 27, 2+7=9, 27-9=18) the remainder is always divisible by 9. The computer puts the same symbol, which changes each time, against all multiples of 9 (9,18,27,36,45,54,63,72,81,90) so no matter what numerical answer you ended up with, the gopher always guesses correctly.