The Story
Where it came from, and why it turned out this way.
DesignClaude Soucie · introduced by Sid Sackson in A Gamut of Games, 1969
A game that came out of a book
Lines of Action was designed by the American Claude Soucie, but what brought it to the world was Sid Sackson's 1969 book A Gamut of Games, a collection of then-obscure abstract games that became one of the founding texts of the modern abstract-games community. Lines of Action is the most widely adopted game in it, and it went on to attract attention in computer game research far out of proportion to its public profile.
One rule that makes capturing a dilemma
The winning condition is not elimination but connecting all your remaining pieces into a single group, which instantly makes capturing dangerous. Every piece you take is one fewer piece your opponent has to connect, and therefore one step closer to their goal. Taken to the extreme, reducing your opponent to a single piece means the rules declare them connected — you have captured your way into a loss. That tension is the pivot of the entire design.
Distance is set by the pieces on the whole line
The other unique mechanism is how far you move: the number of squares a piece travels in a given direction equals the total number of pieces of both colors on the entire line running through it. So the more crowded the board, the further pieces travel, and every capture shortens the distances on several lines and changes every subsequent move. You are not navigating a fixed map — you are navigating one that your own moves keep redrawing.
A regular at computer olympiads
Lines of Action has a moderate branching factor but a genuinely subtle evaluation problem — how do you score "degree of connectedness"? — which has made it a long-running Computer Olympiad event and a classic testbed for game-program research. Work by Mark Winands and others on its search and evaluation functions is widely cited in the design of programs for other abstract games.
- Sid Sackson was a noted designer in his own right, best known for Acquire, and his personal collection of games ran into the tens of thousands — he was among the most important game collectors of the 20th century.
- Rule versions differ on what happens when both sides connect at once: this page defaults to the Soucie variant awarding the win to the player who just moved, while tournament rules score it a draw.
- Because your own pieces can be jumped and enemy pieces cannot, lining your pieces up along one line effectively builds yourself a long-distance corridor.
Complete Rules
Start with what a turn allows and how the game is won.
- Board
- 8 × 8 squares, corners start empty
- Pieces
- 12 discs each, Black moves first
- Winning conditionconnecting all of your remaining pieces into a single group wins, where horizontal, vertical, and diagonal adjacency all count as connections. Note that this is not a game about capturing more — captures are only a means, connection is the end, and having fewer pieces actually makes connecting easier.
- At the start, Black's 12 pieces occupy b through g on ranks 1 and 8, and White's 12 occupy 2 through 7 on files a and h, with the four corners empty. Black moves first.
- Each turn, pick one of your pieces and one of the eight directions. Find the complete row, column, or diagonal that runs through that piece parallel to your chosen direction, count the total number of pieces of both colors on that line as N, and move exactly N squares in that direction — no more and no less.
- The count includes every piece on that entire line: the moving piece itself, enemy pieces, pieces behind the starting square, and pieces beyond the destination. Both directions along the same line share the same N.
- Rows, columns, and the two diagonals are counted independently, and you may never borrow the count from a parallel row or diagonal. A single piece therefore usually has four different distances on its four axes, and the interface lists all four the moment you select it.
- You may jump over any number of your own pieces, but never over an enemy piece. Blocking depends only on the squares between the start and the destination, so an enemy piece behind the starting square contributes to the count without blocking movement in that direction.
- The destination may not hold one of your own pieces. If it holds an enemy piece you capture it and take the square. Capturing is neither mandatory nor always desirable.
- A player whose pieces on the board form one group connected horizontally, vertically, or diagonally wins, with all eight adjacency directions counting. A player down to one piece is treated as already connected.
- After each move and any resulting capture, connectivity is checked before the turn passes. If only one side is connected, that side wins — even if it is the side that did not just move.
Your First Game
Use this order of thought to get through a complete game quickly.
- Rely on the line counts the interface gives you: selecting a piece shows how many pieces sit on its row, its column, its descending diagonal, and its ascending diagonal, and the number matching your chosen direction is exactly how many squares you must move.
- A concrete opening example: Black's b8 sits on file b, which holds only b8 and b1, so vertically it must move exactly two squares to b6. That same piece sits on rank 8 with six black pieces, so horizontally it must move a full six squares at once.
- Do not compute distance as "up to the nearest piece." Distance has nothing to do with what lies ahead and everything to do with the total count on the whole line — and if the resulting destination falls off the board, that direction simply has no legal move.
- Check all eight directions every turn. Diagonal contact counts as connection too, and a great many merging opportunities come from diagonals rather than rows and columns.
- Prefer bringing isolated edge pieces toward your main group over rushing to capture. Joining two sizeable groups is usually worth more than removing one enemy piece.
- Before you capture, look at your opponent: removing one of their isolated pieces may be exactly what turns their remainder into a single group and hands them an immediate win.
Practical Strategy
Move from knowing the rules to playing with a plan.
- Evaluate the position by connected groups first: count how many groups each side is split into and how large the biggest one is. The information panel shows both players' group counts directly.
- Piece count is not a measure of advantage in this game. Fewer pieces are easier to connect, and being reduced to a single piece counts as connected and wins outright.
- Every capture reduces the piece total on several lines by one, which changes every future movement distance along those lines. Before capturing, work out whether it opens or closes your own routes.
- Your own pieces can be jumped, so lining your pieces up on the same line effectively builds yourself a long-distance corridor — while an enemy piece on that line cuts the corridor in half.
- Central pieces sit on longer lines in all four directions, which gives them more available directions and makes them better junctions for several connection routes at once.
- When building a connection threat, watch your opponent's reply: if they are forced to capture or forced to reposition, that forced move may complete their own merge instead.
- Calculate endgames in the right order — check whether you are connected on the imagined post-move board first, then check your opponent. Watching only your own group is how won games get thrown away.
Winning and Special Rules
Details that are easy to miss but can change the result.
- When both sides become connected on the same move, the outcome is decided by an option in the shared panel: the default Soucie variant awards the win to the player who just moved, while tournament rules score it a draw. Changing the option starts a new game and cannot be done mid-game.
- Your opponent's move can win the game for you outright: if capturing one of your isolated pieces leaves your remainder forming a single group, the victory is immediately yours.
- When the side to move has no legal move with any piece, they must pass, and the interface shows a no-legal-move skip button. Passing voluntarily while legal moves exist is not allowed.
- The third occurrence of the same board configuration with the same side to move is a draw. The three occurrences need not be consecutive, and positions produced by a forced pass count as well. Forced passing and threefold repetition are this site's digital anti-loop adjudications.
Common Mistakes
The traps new players fall into most often.
- Computing the move distance as the gap to the nearest piece, or leaving out pieces beyond the destination and behind the starting square.
- Jumping over an enemy piece. Enemy pieces can only be captured by landing exactly on them, never leapt over en route.
- Checking only orthogonal adjacency and assuming two diagonally touching groups are still separate.
- Capturing for its own sake, which neither improves your connectivity nor prevents your opponent's remaining pieces from clustering more easily.
- Forgetting to recount the line after switching directions. A different direction means a different distance, and the number from your last calculation does not carry over.