Zumo is a game of energy transposition for two players: Black and White. It is played on the cells of an initially empty hexhex board. The recommended board sizes are between base-6 and base-10. Each player must have access to a sufficient number of stones in his colour.


Play Zumo interactively


Definitions

• A 'friendly sightline' of an occupied cell is a cardinal line along which a friendly stone can be seen, with only vacant cells in between, adjacency included.
• A 'neutral sightline' of an occupied cell is a cardinal line along which the edge of the board can be seen with all cells being vacant.
• An 'opposing sightline' of an occupied cell is a cardinal line along which an opponent's stone can be seen, with only vacant cells in between, adjacency included.

Play Black plays first, subject to a swap option by White, then turns alternate. The first placement of each player is free. On subsequent turns you must: Place a stone of your colour on an empty cell in such a way that it has at least one friendly sightline. Now the stone automatically sucks in one unit of energy along every friendly sightline. This is indicated by moving every friendly stone in sight one step towards the placed stone. If a stone is placed adjacent to a friendly stone then this stone cannot move further towards it. Instead it 'moves' onto the cell of the placed stone and evaporates in the process. In other words: it disappears. But just as any other friendly stone in sight, it delivers one unit of energy to the placed stone. The diagram shows the process: the white stone is placed at J11 and the three friendly stones in sight all move one step closer.

The placed stone now has 3 energy units which it optionally may use one by one to move opposing stones away from it along opposing sightlines. In the example 3 steps along the red line are indicated, pushing the black stone to J16. But energy units may be distributed in any combination over any or all opposing sightlines. In doing so, any stones that a pushed stone may encounter, whether black or white, are removed from the board in the process.

Theoretically a player may encounter a position in which he has one stone left, that is tightly surrounded by opponent's stones. He then is unable to place a stone and thus must pass.

3-fold
A 3-fold repetion of the same position with the same player to move is not allowed. The applet will take care of it.

Goal
The first player to push an opposing stone over the edge wins.



How I invented ... Zumo


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