Sannin Shogi - Movement On A Hexagonal Board

Movement On A Hexagonal Board

Because each cell of a sannin shogi board is a hexagon rather than a rectangle as in other shogi variants, the pieces will necessarily move differently. Instead of four faces with adjacent squares and four corners, for eight directions total, there are six each for a total of twelve. However, except for castling and the promoted king, which is reminiscent of the queen of Western chess (indeed, it moves like the queen in Gliński's hexagonal chess), the pieces are fair analogues of their standard-shōgi counterparts.

Except when castling, all pieces move in straight lines. These may be step moves, where a piece moves to the nearest cell in a particular direction, or ranging moves, where a piece may continue in a particular direction as long as it does not pass through an occupied cell.

There are two kinds of paths along which pieces move:

• Passing through one of the faces of the starting cell to one of the six adjacent cells, or through this adjacent cell to continue straight in that direction. These six contiguous paths are called orthogonals in this article. They are equivalent to the four orthogonal directions on a rectangular board.
• Passing through one of the corners of the starting cell and between two adjacent cells to reach one of the six cells just beyond, or continuing in a straight line in that direction, alternatingly passing through and passing between the cells. These six skipping paths are called diagonals in this article. They are equivalent to the four diagonal directions on a rectangular board. A piece may travel along a diagonal even if the adjacent cells it passes between are occupied, since it doesn't actually pass through these adjacent cells, and this is not considered a jump, just as on a rectangular board. There are no jumping moves in sannin shogi except for the king when castling.

These twelve directions correspond to the twelve hours on a clock: The orthogonals correspond to the odd hours (the direction of the hour hand at 1, 3, 5, 7, 9, and 11 o'clock), and the diagonals correspond to the even hours (the hour hand at 12, 2, 4, 6, 8, and 10 o'clock). Only the promoted king has the power to move in all twelve.