Normal sudoku rules apply. The digits along each coloured route can be read as a 6-digit 'route number', starting at the square and finishing at the spot. These nine route numbers can be ranked from lowest to highest. A circled yellow taxi on a route indicates that route's rank. (A '1' taxi would be on the route with the smallest 6-digit route number. None of the route numbers are the same, so there are no tied ranks.) Box borders divide a BLUE ROUTE into segments whose digits have the same sum. Adjacent digits on a GREEN ROUTE have a difference of at least 5. Digits on a PINK ROUTE form a non-repeating, consecutive set in some order.