Several versions exist. Instead of determining the winner by scoring primitive rules let the first player without an available move lose the game. Such rules omit passes.
Games tend to be very long and are so called pass fights.
Their final stage consists of suicides respectively attempts to prohibit those of the opponent. They are important in mathematics. The two colour game is played on a finite graph. Play is alternate colouring of a non-coloured node with black respectively white. A play of a colour causes loss of the other colour of all nodes without a path along the other colour to no colour and subsequently causes a loss of the colour of all nodes without a path along the colour to no colour.