Mill is a game of three-in-a-line played on three nested squares. It starts quietly, with both players setting men down one by one, and then turns sharp the moment pieces begin to slide. Pick nine, six or twelve men and a computer level, or hand the screen to a friend.
Rules
The board has 24 points joined by lines. Light moves first. In the placement phase each player puts one man on any empty point per turn until all of them are on the board: nine each in the standard game, six on the smaller two-square board, twelve on the board with diagonals.
Line up three of your men along one straight line and you have a mill; each new mill lets you lift one enemy man off the board. Men sitting in a mill are protected, unless the opponent has nothing outside mills. A move that completes two mills at once still earns a single capture.
Once every man is down, the movement phase starts and each turn slides one of your men along a line onto the free point next to it. Fall to two men, or find yourself without a legal move, and the game is lost. With flying enabled, a side reduced to exactly three men may jump to any vacant point; flying is on by default with nine or twelve men and off with six. A draw is declared after a hundred moves without a capture or when one position appears for the third time, and on the twelve-men board also when placement fills every point.
Strategy
Mobility beats early mills. A mill closed in the first few turns often leaves your men bunched on one side. Prefer the middle points of the four sides, which have three or four neighbours, over the corners, which have two.
Plan for the second phase while placing. Every man you put down will have to move later. Leave yourself empty points to slide into, and try to place so that the opponent's men end up hemmed in. A player who cannot move loses, even with nine men on the board.
Set up a grinding mill. The deadliest shape of the movement phase is a mill you can open and shut at will: one man swings out to a neighbouring point and back, and every return captures. A pair of mills sharing a point works the same way, shuttling in the other direction.
Watch the flying endgame. Once a side is down to three men and can fly, any two of its men in a line are an instant threat. With three men of your own you can no longer block everything, so count threats before you take the last-but-one piece.
Questions
Is mill the same as nine men's morris?
Yes. Mill, merels and nine men's morris are names for the same game. The six-men version uses only two squares and no flying; the twelve-men version adds diagonal lines.
Can I take a man out of a mill?
Only if all of the opponent's men are inside mills. As long as one of them stands outside, an unprotected man is what you have to take.
What happens if both players have only three men?
With flying on, both may jump anywhere, and the game becomes a race of threats. If nobody can force a mill, the hundred-move rule or a repeated position ends it as a draw.
Which level should I start with?
Beginner lets you learn the two phases without being punished at once. Strong already plays the placement phase well, and Master is a hard opponent even for experienced players.
Is mill solved?
Nine men's morris is known to be a draw with perfect play from both sides, which is why games between careful players are often long and tight.