Crossings (game)

Crossings is a two-player abstract strategy board game invented by Robert Abbott. The rules were published in Sid Sackson's A Gamut of Games. Crossings eventually evolved into the game called Epaminondas, but its rules are different enough to make the gameplay significantly different than that in Epaminondas.

Crossings is played on an 8x8 board, with an initial setup as follows; number signs are black stones, zeroes are white stones, and periods are empty spaces:

######## ######## ........ ........ ........ ........ 00000000 00000000

White begins the game, and after that play alternates, one move per player.

In Crossings, a group is a series of same-colour stones adjacent to one another in a line, whether horizontal or vertical or diagonal. Single stones can be considered a one-element group, but the rules in A Gamut of Games treat them separately. Note that a given stone may belong to one or more groups.

Play is as follows:

On their turn, a player may move a single stone, an entire group, or part of a group.
If a single stone is moved, it may move one space horizontally, vertically, or diagonally; its destination must be empty.
If a group is moved, it must move along the line which defines it; it may move a number of spaces equal to the number of pieces in the group.
If a part of a group is moved, it must move along the line which defines it; it may move a number of spaces equal to the number of pieces in the subgroup.
Pieces may not move across or over each other. When a part of a group is moved, it must be one of the two ends.
If the first stone in a moving group encounters a singleton stone of their oponent, the group's movement stops there, and the opponent's stone is captured.
If the first stone in a moving group encounters the "front" stone of an opponent's group, it can capture it if and only if the opponent's group is smaller. It can only capture the first stone, and the movement of the group stops there. If it cannot capture the stone due to the opponent's group being the same size or larger, it is not allowed to move that far.

A player potentially wins the game if they get a stone on the home row, or row farthest from their side. If their opponent cannot get a stone of their own onto the first player's home row in their next move, the first player wins. Otherwise those stones are "locked"; they cannot be moved or captured. The next attempt at crossing, as this is called, will determine the winner (unless it, too, is immediately followed by a counter-crossing, and so on.)

Note that the game may suffer from the same symmetric issues as Epaminondas, and can result in a tie if, somehow, all eight home-row spaces on both sides hold the result of crossings and counter-crossings. This is undoubtedly extremely rare in actual play, however.

References

Sackson, Sid. A Gamut of Games. ISBN 0-486-27347-4
Schmittberger, R. Wayne. New Rules for Classic Games. ISBN 0-471-53621-0