Checkers

American rules · 8 × 8

Black to move

12Black

12White

Opponent

Show legal moves Show square numbers

How to play

Only the dark squares are used. Each side starts with 12 men on the three rows nearest to them. Black moves first, then turns alternate.
A man moves one square diagonally forward to an empty square.
If an enemy piece is diagonally next to yours and the square beyond it is empty, you jump over it and remove it. Capturing is compulsory, and if the piece that jumped can jump again, it must keep going. Jumps can change direction.
If you have more than one capture, you may pick any of them. You don't have to pick the one that takes the most pieces.
A man that reaches the far row is crowned a king (shown as two stacked pieces). Kings move and capture both forwards and backwards.
You lose when you have no legal move: every piece is captured or blocked. Three repeats of the same position, or 40 moves each with no capture or man move, is a draw.
Russian and Malaysian rules change some of this — see the two sections below.

Malaysian rules (Dam)

Played in Malaysia and Singapore, also called Dam or Dum. The board is 12 × 12 with 30 men each on the five rows nearest you — or 8 × 8 with twelve, if that's the board you have.
Men never go backwards, not even to capture. Kings fly: any distance along a diagonal, and they may stop on any empty square past the piece they take.
Take as many as you can. You choose which piece jumps, but that piece must then make the longest jump it has.
Turn a jump down and you lose the piece. Move somewhere else instead and the piece that should have jumped is taken off the board. If several could jump, the one with the biggest jump goes; if the piece that walks away is the one that should have jumped, it is the one you lose.
A man is crowned only if it stops on the far row at the end of its turn. Captured pieces stay put until the move is over, so none of them can be jumped twice.
You lose when you have no legal move left.

Russian rules

Men capture backwards as well as forwards, but they still only move forwards.
Flying kings. A king slides any distance along a diagonal. It can capture a piece from far away and land on any empty square beyond it. If one of those landing squares lets it keep capturing, it must land there.
A man that reaches the far row in the middle of a capture is crowned at once and keeps capturing as a king.
Captured pieces stay on the board until the move ends. You can't jump the same piece twice.

How the computer plays

Search. Uses alpha-beta search with iterative deepening and a transposition table. It always searches forced captures to the end.
Evaluation. Counts material (kings are worth more, especially flying ones), advancement, a guarded back row, control of the centre, and runaway men with a clear path to the crown.
Endgames. When it is ahead it trades pieces off and moves its kings towards yours. When it is behind it heads for the double corners.
Levels. Easy looks a few moves ahead and sometimes slips. Medium thinks for about half a second. Hard thinks for about two seconds, which often means 14 or more plies.
The big board. Under Malaysian rules there are sixty pieces and a jump can be turned down, so there is far more to look at and the computer sees fewer moves ahead than it does on the small board.