Help For HexEmergo

Introduction

hexemergo challenge userid1 userid2 [ -alternate ]

Start a game between userid1 and userid2.

The -alternate option starts the game with the pieces already arranged on the board, in order to reduce the advantage of moving first.

Note: 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

This diagram shows the board, which by default is initially empty.

            1   2   3   4   

      A - .   .   .   .   5   

    B - .   .   .   .   .   6   

  C - .   .   .   .   .   .   7   

D - .   .   .   .   .   .   .   

  E - .   .   .   .   .   .   

    F - .   .   .   .   .   

      G - .   .   .   .   

  Ohs (Ohs) inhand: 12
  Eks (Eks) inhand: 12

• There are two players, 'black' and 'white'. Each initially has twelve men 'in hand'.

• A piece is a column of one or more men, composed in one of the following ways:
  • All white
  • White with black prisoner(s)
  • All black
  • Black with white prisoner(s)

• The top man of a column determines its owner. The top men together are called the cap.

• Players move, and must move, in turn. White moves first. A 'move' may be:
  • Entering a man.
  • Entering the shadowpiece.
  • Moving a piece.
  • Capturing one or more men.

• There are two phases: the entering phase and the movement phase.

Capture

• Capture is obligatory and has precedence in both phases.

• A player captures the top man of an opponent's piece on an adjacent square, by jumping the piece with his own piece, taking the top man along under it, and landing on the square beyond, which must exist and be vacant for the capture to take place.

• Majority capture takes precedence: if the capturing piece can continue its course in a similar fashion in any direction except a 180o turn, it must do so, taking care beforehand to establish the route that brings the maximum number of captured men. If there are more than one way to meet this criterion, the player is free to choose.

• In a multiple capture the capturing piece may visit a square more than once as well as jump a piece more than once!

The capture of a single man reduces the number of pieces on the board by one. Since there is no mechanism to increase the number of pieces, a game of HexEmergo is always 'spiraling upward', that is, the number of pieces steadily decreases while their size increases.

The Entering Stage

• Entering is only allowed on vacant squares. If the player to move cannot make a capture, then entering a man has precedence over moving a piece. He may not enter more than one man, unless his opponent has all twelve men on the board, in which case he must enter his remaining men as one piece. This piece is called the shadowpiece.

A player may still have several men in hand while his opponent has all men on the board. This is always the result of one player entering while the other must capture. It is not at all unusual: creating a large shadowpiece is a very valid strategic goal, particularly for black.

White may not, on his very first move, enter on the central square (e5). Apart from that there's only one condition for entering a man or the shadowpiece alike:

• Entering may not force an opponent into making a capture, unless the entering player is already being attacked by his opponent.

This is the key rule governing the entering phase! As long as my opponent does not attack any of my pieces, I may not put the piece I enter under attack. If he attacks one of my pieces, however, he releases me from the above condition.

The MovementStage

Alternative Rules

            1   2   3   4   

      A - X   X   X   X   5   

    B - X   X   X   X   X   6   

  C - .   X   X   X   X   .   7   

D - .   .   .   .   .   .   .   

  E - .   O   O   O   O   .   

    F - O   O   O   O   O   

      G - O   O   O   O   

Initial board with -alternate option.

There is no entering stage. White simply starts under the rules of the movement stage. Note that both players have thirteen men instead of the usual twelve.

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