Diamond
The game commences with the board vacant of counters.
No. of Players
Two
Equipment
A Diamond gameboard, twelve each of black and white counters, and some neutral red counters are required for play. The counters are played at the vertices (nodes) of the gameboard.
History
Diamond was inspired by the game Kensington and conceived in 1985 by Larry Back, but was not finalized until 1994. Diamond was featured in the February 2013 issue of Games magazine.
Objective
A player wins by being the first to occupy all four corners (points) of a board square with their counters. Draws may occur upon agreement by both players; when it is a player's turn and he is unable to make a legal move; when the exact same board position has been repeated three or more times; or if no capture has been made or neutral counter has been removed for 50 turns (25 moves per player).
Play
The game commences with the board vacant of counters. Alternating turns commence with black moving first. The Pie Rule is implemented, meaning that the player that chose to play white may switch to black after the first move. Passing on a turn is not permitted. The game is executed in two phases. In the first phase of the game, alternate turns entail the placement of a single friendly counter at any of the vacant vertices on the board. A player may win the game during the placement phase if she manages to occupy all four corners of a square on the board with four of her counters. Otherwise, the second phase of movement begins. During the movement phase a player may either move one friendly counter to an adjacent vacant intersection, in any direction, or remove a red neutral counter from the board, provided that it is not adjacent to any black or white counters.
It is also possible to capture opposing counters in the movement phase. If the points of a triangle contain exactly one white and one black counter, either player can capture the opposing counter by moving to occupy the remaining vacant point ("cornering" the opposing counter on the triangle). The captured piece can be cornered on one triangle (need diagram), or simultaneously cornered on two different triangles (need diagram). The captured counter is immediately removed from the game and replaced on its point by a neutral red counter.
If a move simultaneously corners two opposing counters on two different triangles, then neither opposing counter is captured (need diagram). A counter can move safely to a triangle point even if the other two points of the triangle are occupied by opposing counters (need diagram).
Variations
Diamond was inspired by the game Kensington. Onyx is a connection game, also invented by Larry Back.
Sources
Back, Larry (February 2013). Schmittberger, R. Wayne; Orehowsky, Jennifer, eds. "Diamond: A Strategy Game for Two Players". Games. Games Publications (287): 58, 65–67. ISSN 0199-9788