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 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.