Uknight is a unification game based on the hexagonal knight's move. By its nature it is a distant descendant of Lines of Action and a direct descendant of KnightVision.

Play Uknight interactively


Material
A base-5, -6 or -7 hexhex board and a sufficient amount of red and white stones.

Definition
A group is a stone together with all like coloured stones that can be reached from it by taking single steps to cells sharing an edge and holding like coloured stones.

Rules
On his turn a player may always:

• Remove every isolated single stone of his own colour of which all cells at a knight's move distance are occupied by the opponent. This may be done in any turn, before any placement or movement or axe-throwing occurs.

The diagram shows a board with six stones of each colour in their initial position. The pie rule is operational so after the first White placement, Black either accepts it as his first move, or places a black stone. After that turns alternate. Using a turn fully, or partly, or not at all, is optional.

Phases
The game has two phases separated by the first simultaneous presence of a required number of axes on the board, regardless of who owns them:

• 4 axes on a base-5 board of 61 cells
• 6 axes on a base-6 board of 91 cells
• 8 axes on a base-7 board of 127 cells

Before that point has been reached, a turns consists of:

• placing of a single stone on a vacant cell, or
• throwing an axe

How axes emerge is explained below. However, so long as the required number of axes has not been reached, an axe may NOT capture an opponent's piece that also carries an axe. After reaching the required number, axes do no longer suffer this restriction, but now further placements are forbidden and instead stones that are already on the board may be moved using the knight's move.

Options in the first phase In the first phase a player may: Place a stone of his colour. The stone must be placed a knight's move away from at least one friendly stone. Example: A knight's move away from the white stone at B1 we find E2, E3, D4, C4 and A3. Axes If a stone is placed on a cell that is at a knight's move distance of at least three friendly stones, it gets an axe, indicated by a dot. Example: If White makes his first placement at A3 then a next white placement at D4 gives an axe.

Options in the the second phase
If a placement results in the required number of axes appearing on the board, counting those of both players', then moving becomes the only alternative for throwing an axe and the opponent therefore has the first chance to do so.The second phase is permanent, regardless of axes that may appear or disappear afterwards. Placement is now illegal.

• Players may move a stone of their own colour to a vacant cell at a knight's move distance. The stone may or may not hold an axe. If on arrival at its destination cell a stone without an axe finds itself at a knight's move distance of at least three friendly stones, then it gets an axe, just like a placed stone.

Throwing axes around
A player can always use a turn to throw an axe if he has one. An axe is thrown in a straight line in any of the three cardinal directions. On its departure cell a regular stone remains in place. The axe moves any distance, stopping at will on any vacant cell or at the first opponent's piece, stone or double, it encounters. It then captures that piece and replaces it by the same piece of its own colour, stone for stone, double for double.

Goal
The first player who unites all his pieces, with or without axes, in one group, down to and including a single piece, wins the game.




How I invented ... Uknight


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