The nine-men's morris is filled up with mud;
And the quaint mazes in the wanton green,
For lack of tread, are indistinguishable.
   – Midsummer Night's Dream (Act 2, scene 1), Shakespeare

Two persons, having each of them nine pieces, or men, lay them down alternately, one by one upon the spots; and the business of either party is to prevent his antagonist from placing three of his pieces so as to form a row of three, without the intervention of an opponent piece. If a row be formed, he that made it is at liberty to take up one of his competitor's pieces from any part he thinks most to his advantage; excepting he has made a row, which must not be touched if he have another piece upon the board that is not a component part of that row. When all the pieces are laid down, they are played backwards and forwards, in any direction that the lines run, but only can move from one spot to another (next to it) at one time. He that takes off all his antagonist's pieces is the conqueror.