Nine Men's Morris

Three in a row is a mill — and a mill takes one of theirs

Players

Play

Opponent

Strength

Board

Flying on three menDown to your last three, a man may jump to any empty point. Show where I can go

Moves

How to play

The board is twenty-four points where the lines meet. You each have nine men, and the game comes in three parts.
Placing. Take turns putting a man on any empty point until all eighteen are down.
Moving. After that, a turn is sliding one of your men along a line to an empty point next to it.
Mills. Three of your men in a row along one line is a mill — and whenever you make one, you take one of your opponent's men off the board, for good.
You may not take a man that stands in a mill, unless every man they have left is in one.
Open a mill and close it again next turn and it counts afresh, so a pair of mills you can swing a man between — an open mill — takes a man every single turn.
Winning. Reduce your opponent to two men, or leave them with no legal move, and the game is yours.
Flying: down to their last three men a player may jump to any empty point rather than slide. It is the usual rule, and you can switch it off above for the harder, older game.
The game is a draw if the same position comes round three times, or if fifty moves pass with nobody taking a man.
Six and Twelve Men's Morris are the same game on a smaller board and on this one with its diagonals drawn in. Six has no middle ring and no mills through the middle; twelve adds four diagonal mills and fills the board almost solid.
How the computer plays: it searches ahead move by move, further the longer it is given, and weighs up mills made, mills one man short, men it has penned in and moves each side can still make. Hard looks several moves deep and sees an open mill coming; Easy takes the men it can see and little more.
Online friend sends a link. You each move on your own device, and the two boards follow the same list of moves, so they cannot disagree.

Strategy

Take the crossings. The four points in the middle of each side touch four lines; corners touch only two. Men on crossings can do twice as much.
Build two mills that share a man while placing. Once the sliding starts, that one man swinging in and out takes a piece every turn and the game is over quickly.
Don't rush the first mill. A mill made early is often a mill locked in place — three men that cannot move are three men not playing.
Take their freedom, not just their men. Reducing an opponent to a few legal moves wins as surely as reducing them to two men.
Count the men you can take. Break a mill of theirs when you can: a man in a mill is safe from you until everything else is gone.
Stuck? Hint plays the move the Hard computer would choose.