Lines of Action

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Starting position, Black to move [1]

Lines of Action, (LoA)
a two-player zero-sum and perfect information abstract strategy board game, a connection game played on a standard chessboard, with two times six pieces or checkers per side, White and Black. The goal is to connect all of one's pieces into a single group. Checkers alternately (starting with Black) move horizontally, vertically, or diagonally like a queen in chess, but exactly as many spaces as there are own and opponent checkers on the line. Opponent checkers may be captured, but not own ones, checkers may jump over friendly but not over opponent ones.

A Gamut of Games

Lines of Action was invented by Claude Soucie around 1960, [2] , described 1969 by Sid Sackson in A Gamut of Games, and published in 1988 by Hexagames. Since 1997, human players annually compete at the world championship as part of the Mind Sports Olympiad, Lines of Action programs regularly at the Computer Olympiad, organized by the ICGA.


In his thesis, Mark Winands lists a state-space complexity of about 1.3 x 1024 positions, an average branching factor of 30, and a game-tree complexity of 1056 positions [3].

Computer Olympiads



London 2000, first medals in LoA: Mark Winands (B), Yngvi Björnsson (G), Darse Billings (S) [4]


LOA winners of the 8th Computer Olympiad: Bernard Helmstetter, Mark Winands and Jun Nagashima [5]

Selected Publications

2000 ...





2005 ...

2010 ...

External Links


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