Gordon Shumway: The ability to leave an empty spot is identical to adding another colour.
The general formula for the number of codes with N spots and C colours is CN for regular logic; for unique logic, the formula is C!/(C-N)!, assuming there are at least as many colours as there are spots (otherwise, you wouldn't have any possible codes).
(hide) Tired of placing boats or Espionage pieces at the begining of the game? You can go to Game Editors and save some of your favourite positions for future use. (pauloaguia) (show all tips)