The Game of JadeJack

This is the game of JadeJack that appeared originally as Hi-Jack in issue 14 of the Abstract Games magazine [ www.abstractgames.org ]. It is a game of territory, and is played with disks that may stack. The territory count is determined by the strengths that are exerted by the occupied squares. If you are looking for a game that offers a novel playing experience, with plenty of drama and deep tactical conflicts then please read on.

For the latest rules go to [ www.efbweb.uwclub.net ].

( A game in progress. Black to move. The X's indicate the playable squares. )

The Game

The game can be played on a range of board sizes. Minimum 8x8.

Two players. Two colours. Black goes first. Both take turns to place a disk of their colour on the board.

Strength, Placement. All occupied squares on the board have strength which extends to neighbouring squares. The strengths determine where moves may be made and if stacks of disks can be 'turned' ( see later sections on strength and placement ).

Passing. Passing of moves is permitted. If both players pass then the game comes to an end.

No Move. If a player can make no move then he has to pass his go.

No Centre First Move. The first move of the game may not be made in the centre. For 9x9 and 11x11, the centre square. For 10x10, the four middle squares.

Scoring. A player's score is the number of unoccupied squares over which he has greater strength than the other player. The winner is the player who has the greater number.

Komi. To counter the first move advantage that the first player has the second player is given a komi score of 1.5 points. A game cannot end in a draw. If a game ends with all squares occupied then the second player ( White ) will win because of the komi.

Territorial Strengths

Extending the Strength. A lone disk adds a unit of strength one square in each orthogonal direction. A 2-high stack adds one unit to two squares in each orthogonal direction. A 3-high stack adds to three squares in each orthogonal direction and one square in each diagonal direction. Higher stacks progressively extend one more square in all directions.

Blocked Strengths. Strengths are applied to all squares, occupied or not. However, a strength along an extended line is dropped if all intervening squares are occupied.

( Territorial strengths )

( Blocked strengths. The stacked squares add no strength to squares marked 'o'. Intervening squares are occupied. )

Placement

Unoccupied Square. You may play a disk onto an unoccupied square only if your strength at that square is at least equal to that of the other player.

Hijacking. You may play a disk onto a square that the other player holds only if your strength at that square is at least equal to that of the other player plus the height on the square. The square gains one level in height and becomes yours.

Self Stacking. You may play a disk to a square that you already hold. Either onto a lone disk. Or else onto a stack, but only if there is only one of your disks at the head of the stack; that is to a square you have hijacked and to which you have not yet played an additional disk. Self stacking on a square can be made regardless of the strengths that each side has on that square.

Re-Hijacking. Squares may be re-hijacked. There is no limit to the number of disks that may stack on a square.

( Black and White both have three units of strength on the triangled square. Either side may play there. Note that the strength from White's bottom 2-stack is blocked. Black's strength from the right hand 3-stack is not blocked. Black also has a unit of strength diagonally from the other 3-stack. )

Suggestions for Rule changes

Here are some changes that I would like to propose.

No Diagonal Strengths. Restrict strength extensions to orthogonal directions only. Diagonals seem unnecessary. You will rarely get a 3-stack at the front of a group since a competent player will never allow a good square to be hijacked. 4-stacks are rarer still. And trials seem to show that within a group strengths diagonally extended from a 3-stack have little influence.

Strength Blocking. Extend strengths along a line only as far as the first occupied square. Strengths beyond a blocked square are not seen that often and would require the stack to be at least 3-high. This change would also simplify the wording of the rules.

Reducing the influence of 3-stacks and higher might make for more interesting positions. Players might be more willing to sacrifice a square in return for a big move elsewhere.

Centre Square. First player may not make the first move in the centre.

Penalty Squares. Designate certain squares as penalty squares, with values 1, 2 or 3. Your score is decreased when you have strength over these squares. The squares must be kept free. You may not play in any of them.

Double, Triple Score Squares. Designate certain squares as bonus value squares. Gaining the greater strength over these squares gives you 2, 3 points. The squares must be kept free. You may not play in any of them.

Minority Squares. This is a new idea. This rule will shorten the game and will make it easier for the players to create and hold bigger regions of territory. To an unoccupied square at the edge of the board where you have no strength and where the neighbouring squares in the orthogonal directions are all unoccupied, you may play only if you have at least equality in strength in the neighbouring squares. In short, you may not play on a square that is within the guard of the other player.

( The rule forbids White from playing on any of the triangled squares. White has fewer choice of moves. Black has more chance to get and keep regions of territory, but White can still invade the top corners by playing in the corners marked 'C' since Black has no strength on the neighbouring squares. )

( Black can claim a corner worth five points with just two moves. Under the standard rules White could invade and erase the corner territory. )

Online Play

The game may be played online on my game server, Gorrion. Board sizes are 9x9 and 10x10. I am 'dashstofsk' at the server and will welcome challenges. The program calculates the scores after each move and also highlights the playable squares that are available to you.

[ http://www.dashstofsk.net/gorrion.php ].