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Crossfire
Crossfire is derived from Sid Sackson's game "Focus", also known as "Domination".
It's predecessor features rather capricious tactics, involving the building of stacks of men, and Crossfire
follows suit. Yet, apart from the obvious difference of Focus being played on a square tesselation and
Crossfire on a hexagonal one, there's one big difference: in Focus the 'capacity' of every square -
the maximum stack it will hold - is five men. Any stack surpassing this number
is reduced to five by taking the excess from underneath, whereby the opponent's men are captured,
and friendly men are kept as 'reserves' that may be re-entered on the board. In Crossfire the capacity of a cell
equals the number of adjacent cells! Corners will hold at most a stack of two, sides at most three
or five, and cells of the inner area at most six. This gives rise to a strategy not possible in Focus:
moving big stacks onto 'low-capacity' cells, corners in particular. Thus considerable numbers of prisoners
can be made and reserves created on fixed target cells. In Focus for instance one can never make prisoners,
nor create reserves, by moving a stack onto a vacant square. In Crossfire, moving a stack of five onto a
vacant corner renders three men. This fixed element makes Crossfire more of a strategy game than its illustrious
predecessor.
Rules
If there's mention of men and pieces, a man is single,
while a piece consists of a number of stacked men. If the difference doesn't matter,
a man may also be referred to as a piece, for instance 'the number of pieces on the board'.
Object
- If a player has no legal move he loses the game
The first diagram shows the board, with the pieces in the initial position. The coordinates of a cell can be
found by looking along the files to the bottom-left and bottom-right respectively, to obtain the letter and number.
- There are two players, 'black' and 'white'
- Players move, and must move, in turn. White moves first
- A piece consists of one or more stacked men
- A piece may be mixed in any way. The top man of a piece determines its owner
- Players may only move their own pieces
- A move consists of either:
-
picking up the piece - or any number of top men of the piece - and moving it the number of cells
equal to the number of men that are moved, in one of the six main directions. It does not matter
whether, or by whom, the target cell is occupied
- entering a 'reserve' on any cell
(except if excluded by the ko rule).
It does not matter whether, or by whom, the target cell is occupied
The next diagram shows white's options for the piece of five: he may move the top man onto any of the cells
marked '1', the top two men onto any of the cells marked '2', the top three men onto any of the cells marked '3',
the top four men onto any of the cells marked '4' and the whole stack onto any of the cells marked '5'.
Rules
- The capacity of a cell - the maximum height of the stack it will hold -
equals the number of its adjacent cells. The diagram below gives the capacity of every cell
- If a player's move results in a stack surpassing the capacity of the cell it occupies,
then the player must
remove the excess from underneath the stack. Friendly men thus obtained become part of the player's reserves.
Opponent's men thus obtained become prisoners and are removed from play
If you considers once again
white's movement options in the second diagram,
you'll see that moving the entire stack 5 cells horizontally to i7 leads to a stack of 5 on a
two-capacity cell, and thus to an 'overcapacity' of three men. These three men - two prisoners and one reserve -
are removed from under the stack in the same turn. The remainder, a stack of two white men, remains on i7.
The Ko Rule
- A player may not create the same position with the same move twice
The next example is not meant to illustrate any strategy, only the mechanics involved. Other pieces, prisoners and
reserves have been left out for clarity. Let's assume that white has created a stack of six by moving a
white-black-white stack onto a black-white-black one, and that black has next put a reserve on top of
a white-black one and removed a reserve from underneath. It is now white's turn. If he
enters on g3, he immediately regains his reserve, which means that he effectively only reverses the colors
of the stack. Now black cannot enter on g3 because he would, with the same move, recreate a position that
already occured! But black can enter on top of the six, also immediately regaining the reserve and effectively
only reversing the colors of the stack. The difference is that white now still can enter on the six.
Although he does recreate a position that already occured, he does so with a different move (since he first created
the stack by moving a white-black-white stack onto a black-white-black one). Black now of course cannot
enter on either stack, though he may do so as soon the position as a whole, which isn't depicted here, has changed.
The ko-rule has been introduced for precisely the type of situation depicted here: even numbered maximum capacity
stacks with alternating colors that, by nature, can be reversed while all else remains exactly the same. Of course
there are other scenario's in which it may apply because the mechanics do not prevent the possibility of both
players moving to and fro, though it is hard to imagine a position in which this would approximate to sound strategy.
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