Triangular chess (game)

Triangular chess is a chess variant for two players invented by George R. Dekle Sr. in 1986.^[1][2] The game is played on a hexagon-shaped gameboard comprising 96 triangular cells. Each player commands a full set of chess pieces in addition to three extra pawns and a unicorn.

Triangular chess and its variation tri-chess were included in World Game Review No. 10 edited by Michael Keller.^[3]

The starting setup is as shown. As in chess, White moves first, and the object is checkmate. Other standard conventions apply as well, including castling, the pawn's initial two-step move, the en passant capture, and promotion at the last rank. The triangular geometry, however, implies special move patterns for the pieces.

• A rook moves in a straight line starting through a cell edge. (Three directions are possible.)
• A bishop moves in a straight line starting through a cell vertex. (Three directions.)
• The queen moves as a rook or bishop. (Six directions.)
• The king moves one step as a queen. When castling, the king slides two cells if castling short (0-0); three cells if castling long (0-0-0).
• A knight moves in the pattern: two steps as a bishop, then one step as a rook in an orthogonal direction. A knight leaps any intervening men.
• The unicorn moves in the pattern: two steps as a rook, then one step as a rook in an orthogonal direction. Like a knight, the unicorn leaps any intervening men.
• A pawn moves straight forward one step at a time, whether crossing a cell edge or vertex. On its first move it may optionally move two steps straight forward. A pawn captures to either cell adjoining the cell immediately in front, in the same rank.
• If a pawn reaches a board edge where no step straight forward exists, the pawn continues to advance toward promotion using its capture move (whether there are men to capture or not).

Tri-chess is a variation of triangular chess created by Dekle in the same year.^[4][2] The game is for two players and is the same as triangular chess in all respects except the moves of the bishop, rook, queen, and king are increased.

• A bishop moves in six directions constituting board diagonals.
• A rook moves in six directions along horizontal ranks or oblique files.
• The queen moves as a rook or bishop. (Twelve directions.)
• The king moves one step as a bishop or two steps as a rook.

The bishop moves along cells in the diagram colored dark gray.

The rook moves along cells in the diagram colored light gray.

The Tri-Chess king moves one step as a bishop (dark gray cells) or two steps as a rook (light gray cells).

• Also by George Dekle:
  • Masonic chess
  • Tri-chess – a three-player variant with triangular cells
  • Trishogi – a shogi variant with triangular cells

Bibliography

• Keller, Michael, ed. (June 1991). "A Panorama of Chess Variants". World Game Review. No. 10. Michael Keller. ISSN 1041-0546.
• Pritchard, D. B. (1994). The Encyclopedia of Chess Variants. Games & Puzzles Publications. ISBN 0-9524142-0-1.
• Pritchard, D. B. (2007). Beasley, John (ed.). The Classified Encyclopedia of Chess Variants. John Beasley. ISBN 978-0-9555168-0-1.

• Triangular Chess Tri-Chess simple programs by Ed Friedlander (Java)
• Triangular Chess See detailed rule descriptions, piece movements and play this variant on Omnichess