Help for the Game of Halves

Welcome to the network Halves server. The challenge command is described here. Other commands are the same as for all pbmserv games.

  halves challenge
[-tiles_each=number] [-manual_start] [-no_contract] [-invert_win]
  [-must_touch=number] [-touch_any|-touch_enemy] [-free_edges=number]
  [-keep_chosen|-keep_largest|-keep_most_friendly] userid1
userid2 [userid3]

starts a new game for two or three players.

The -tiles_each parameter specifies how many tiles each player starts with (default 12).
The -manual_start option specifies that players place their own tiles rather than starting with a random placement.
The -no_contract parameter specifies that the game is played without a keep/swap contract.
The -invert_win option specifies that the game is won by the last surviving player.
The -must_touch parameter specifies whether tiles must be placed adjacent to one or two existing tiles (default 1).
The -touch_any parameter specifies that can be placed adjacent to any other tiles (default off).
The -touch_enemy parameter specifies whether tiles must be placed adjacent to at least one enemy tile (default on).
The -free_edges parameter specifies the minimum number of free edges a tile must have to be removed (default 0).
The -keep_chosen parameter specifies that the mover chooses which disconnected group survives each turn (default off).
The -keep_largest parameter specifies that the largest disconnected group survives each turn (default on).
The -keep_most_friendly parameter specifies that the disconnected group with the most friendly pieces survives each turn (default off).


Halves is boardless strategy game for two or three players.

A game of Halves is a game of halves: the first half is spent adding pieces while the second half is spent removing pieces. In addition, moves can be used to halve the remaining pieces (or more). The players giveth, and the players taketh away.


Each player starts with 12 hexagonal tiles of their colour in hand.

Waxing phase: All tiles are randomly placed in a single connected group. In real life, this would just involve placing the tiles quickly and without much thought, by either one or both players.

If the manual_start option is specified then the game starts with one of each player's tiles arranged as follows, then players take turns adding a tile of their colour adjacent to at least one enemy tile.

   _____                _____
  /     \              /     \
 /       \            /       \_____
 \       /            \       / _ _ \
  \_____/              \_____/ _ _ _ \
  / . . \              / . . \  _ _  /
 / . . . \            / . . . \_____/
 \  . .  /            \  . .  /
  \_____/              \_____/ 
 Two-player            Three-player
   start                  start

Contract phase: If the game is played with a contract, player A then elects which colour to play and player B makes the next move.

Waning phase: When all tiles have been placed, players take turns removing a tile of their colour. If this removal splits the remaining tiles into two or more disconnected subsets, then the largest subset is kept and all other subsets removed. If there are two equal largest subsets, then the mover chooses which subset survives.

End: The game is won by the first player with no tiles left on the board.


White to move in the waning (i.e. tile removal) stage. Black is two moves away from a win:

                /     \
          _____/       \_____
         /     \       / . . \
   _____/       \_____/ . . . \
  /     \       / . . \  . .  /
 /       \_____/ . . . \_____/
 \       /     \  . .  /
  \_____/       \_____/ 

White removes their central bridging piece to create two disconnected subsets...

                /     \
               /       \_____
               \       / . . \
   _____        \_____/ . . . \
  /     \       / . . \  . .  /
 /       \     / . . . \_____/
 \       /     \  . .  /
  \_____/       \_____/ 

...and removes the smaller (left) subset as part of the move:

                /     \
               /       \_____
               \       / . . \
                \_____/ . . . \
                / . . \  . .  /
               / . . . \_____/
               \  . .  /

White has now turned the game around and will win on their next move.


Disconnect and remove subsets to get rid of as many of your pieces as quickly as possible.

First move advantage: The opening player has an advantage in that they will win if no groups are disconnected. However, this is balanced out somewhat by the second player’s advantage of having last reply to the opening player’s placements; in particular, the second player gets to place the very last tile.

Three-player game: The three-player game is played according to the rules described above. If two players win on the same move then the game is a tie between those two players.

Thanks to Richard Rognlie for suggesting the -invert_win option.


The move syntax is:

  halves move board# userid password 3
  halves move board# userid password 4,2
  halves move board# userid password keep
  halves move board# userid password swap

The first example either places a tile of the current player's colour at position 3 (waxing phase) or removes tile 3 (waning phase).
The second example removes tile 4 and keeps the subgroup containing tile 2. Other subgroups are removed.
The last two examples show how to either keep or swap colours on the contract move.


Halves rules copyright (c) Cameron Browne, October 2007.

Halves was one of those games that occurred in a flash - it took about 15 minutes to think the rules through and jot them down. Some embellishments were considered then abandoned for the sake of simplicity.

Halves is a "take away" reduction game in the style of Nim and Steven Meyers' excellent Forms.

Implementation and Help file by Cameron Browne, October 2007.