Nine Mens Morris

nine men's morris is a strategy board game for two players dating at least to the roman empire. the game is also known as nine man morris mill mills the mill game merels merrills merelles marelles morelles and ninepenny marl.
the players start with nine different colored tokens each. to start the game the players place their tokens on any of the available circles on the board. when all tokens are placed the game enters the second part. players now move their tokens. a token can be moved from one circle to another along the lines. tokens can never be placed or moved to a slot that is already occupied.
whenever a player forms a mill three tokens in a row they can take any opponent's token that doesn't belong to a mill. if all of the opponent's tokens are inside some mill then an exception is made and the player can take any token. in the opening it's possible to form two mills by placing a single token. the player still gets to take only one of the opponent's tokens.
the game is won by bringing the opponent to a position where they cannot move or by reducing them to only two tokens.