Nine Men’s Morris

The game has two halves. In the first, you take turns putting your nine pieces on any empty point — dark places first. In the second, once every piece is down, you take turns sliding one piece along a line to a neighbouring empty point. The lines are the ones drawn on the board: the three rings, and the four spokes that join them at the middle of each side. The corners are not joined to anything across the rings, which surprises almost everybody once.

Whenever you get three of your own pieces along one of those lines you have made a mill, and you immediately take one of your opponent’s pieces off the board. You may not take a piece that is standing in a mill of its own, unless every piece they have left is in one. A mill you already have does not pay again for a move somewhere else — only the piece that completes the line counts.

You lose when you are down to two pieces, or when it is your turn and you have no legal move at all. One exception keeps the ending alive: a player reduced to exactly three pieces may move to any empty point rather than only to a neighbour.

Zerdly uses the standard game: nine pieces each, mills only along the drawn lines, the protection on a milled piece with the all-milled exception, flying at three pieces, and a draw after a hundred turns with nothing taken. There are no house rules to toggle, so a result here means the same thing every time.

While your pieces are in hand a turn is one tap. After that it is two — the piece, then where it goes — and if that closes a mill you are asked which piece to take. The board says which of those it is waiting for, in words above it and in the label a screen reader reads on every point. Picking up the wrong piece costs nothing: tap another one, or tap it again to put it back.

Undo takes back your last move — against the computer it also takes back the reply, since undoing one move would simply hand you the same position. Show move hints and Show coordinates are remembered between visits. Sound can be turned off at any time; nothing in the game is conveyed by sound alone. A game in progress is saved as you play and is waiting when you come back — including a game you are losing.

Versus the computer gives you six strengths. The weaker ones do not merely look less far ahead — they sometimes choose a move they can see is not the best, which is what makes them feel like an opponent rather than a machine with poor eyesight. The strongest never does.

Two players, one device takes the computer out of it entirely. These games are counted but not scored: both players are here, so there is nobody for Zerdly to call the winner.

Puzzle positions are twenty-four endings across three sets: win in one, in two, in three. Each has been solved to prove that exactly one move forces the win and that nothing shorter does, so the answer is a fact rather than an opinion — and a wrong guess costs nothing, moves nothing and is not counted against you.

Take the junctions. The four points in the middle of each side of the middle ring sit on more lines than anything else on the board, and a piece there is part of more possible mills than a piece in a corner.

The prize is not a mill, it is a mill that can open and close. If you can arrange two mills that share two pieces, one piece steps back and forth between them and takes something every single turn. That is very close to winning outright, and it is worth more than being a piece ahead.

Count moves, not pieces, once the placing is over. A player with more pieces and nowhere to put them is losing, because being unable to move is a loss — so blocking is not defensive, it is how the game is won.

The whole game runs in your browser. The opponent thinks on your own device and the puzzles are proved there too, both in background threads so the page stays responsive while they work — which matters most on the very first move, where the opponent has the widest choice of anywhere in the game. No account is needed and nothing about your game is uploaded.

Your record, your saved game, your puzzle progress and your sound, motion and assist settings are stored in this browser only. Nothing here asks for a name or an email, and the button on this page removes all of it — and only this game’s share of it.

Is it really free, and do I need an account?

Yes, and no. There is no sign-up, no trial and nothing to buy. The game runs in your browser and never sends your moves anywhere.

Why can I suddenly not place any more pieces?

Because you have placed all nine. The game has two halves: first you both put your pieces down, then you move them one step along a line. The rail above the board says which half you are in and how many you still have in hand.

Why can I not take that piece?

A piece standing in a completed mill is protected while any of your opponent's other pieces are outside one. If every piece they have is in a mill, the protection lifts and you may take any of them.

Can I play against another person online?

No. Two-player here means two people at the same device, taking turns. There is no matchmaking and no online play, and nothing on this page pretends otherwise.

How strong is the computer?

The weakest level looks one move ahead and often plays something it can see is not best. The strongest looks six moves ahead and never does. The levels were set by timing the search rather than by guessing at it.

Are the puzzle answers actually right?

Yes, and that is checked rather than assumed. Every position is one where a forced win exists, proved by a search that examines every branch instead of pruning — and a second, independent solver re-proves each published answer, including that no other move works and that nothing shorter does.

Why does the puzzle not ask me which piece to take?

Because in these positions it does not matter — every piece you could take after the right move wins. Grading that choice would mark correct answers wrong, so positions where the capture decides the game are left out of the pack entirely.

Where is my progress kept?

In this browser, and nowhere else. Clearing your browser data, or using the button on this page, removes it permanently.

• ReversiSix opponents, an analysis board and solved endgame puzzles.
• Four in a RowSix opponents, a daily position and tactical puzzles.
• CheckersDraughts against the computer or a friend.