The Game of Onyx

Here is an introduction to the game of Onyx. Onyx was invented by Larry Back and first published in the Abstract Games magazine. It is a connection game that allows capture and is played on a geometrical tessellation of triangles and squares. It really deserves to be more widely known.

Onyx is one of the games played online on my game server, Gorrion. Please do join in the fun. I am 'dashstofsk' at the server and will welcome challenges.

[ Gorrion Games Online ]

Two players. One player takes black, the other white. Both take turns to place a piece of their colour on the board shown above and aim to form a connected chain of pieces that links opposite sides of the board. The player with the black pieces aims for a vertical connection, the other player aims for a horizontal connection. The nodes in the corners of the board are common to both adjoining edges. Black ( vertical ) goes first.

The Midpoint Rule.  A player may play at the midpoint of a 'square' only if none of the four corners of the square are occupied. In the following diagram neither player may play on any of the nodes marked A to F. The other midpoint square nodes are playable.

( Invalid midpoint moves. )

The Capture Rule  Pieces can be 'captured' during the course of a game. If the midpoint node of a 'square' is unoccupied a player can capture by completing a configuration in which all four corners of the square are occupied with both players occupying opposite corners of the square. The other player's pieces are then removed from the square. In the following diagram white can play on the node marked A to capture the two black pieces in the square. White can play at B, but this does not capture since the midpoint node is occupied.

( Capture, before and after. )

Double Capture.  A double capture is allowed. In the following diagram white captures four black pieces with one move at the node marked A.

( A double capture, before and after. )

The Swap Rule.  The second player ( white, horizontal ) has the option to swap colours immediately after the first player has made his first move ( black, vertical. ) If swapped the roles will be reversed. The first player will take the white pieces, will have to aim for a horizontal connection and will play against his own first move. The second player is given a swap option in order to counter the first play advantage that the first player would otherwise have.

Variations.  There are two variations. A game can start either with each player having four starting pieces at the edges of the board ( standard variation ) or with an empty board ( open variation ).

( Standard variation. Initial layout with starting pieces. )

Alternative Board Sizes.  Larger boards lead to a deeper game. All these sizes can be played at Gorrion.

Links.  An Abstract Games article about Onyx used to be at [ http://www.abstractgamesmagazine.com/onyx.html ]. An archive copy is available at [ Archive - Onyx ]. The article explains some of the history behind the game and also the logic of adopting the odd looking board and its rules.