Help For Diffusion

Introduction

Welcome to the network Diffusion server. The rules of Diffusion are below. The Diffusion "challenge" command is described here. Other commands are the same for all pbmserv games.

Current games can be viewed here.

diffusion challenge userid1 userid2: Start a new game between userid1 and userid2

Diffusion Rules

AUTHOR'S NOTE: Feel free to distribute this document.

Introduction

Diffusion is a two player game which employs a Mancala board and a set of like-colored stones. Here a 2x6 board with 48 stones will be used. Initially the board is set up with four stones in each of the small pits and no stones in the large pits, as shown in Figure 1. Two 2x3 “blocks” are outlined in Figure 2. Each player owns the block to his left. Numbers indicate the stone count in each pit. Diffusion is a unique, robust addition to the family of Mancala games. Draws and ties cannot occur in Diffusion. Mark Steere invented Diffusion on January 20, 2006.


      F   E   D   C   B   A 
.---.---.---.---.---.---.---.---.
|   | 4 | 4 | 4 | 4 | 4 | 4 |   |
|   |---+---+---+---+---+---|   |
|   | 4 | 4 | 4 | 4 | 4 | 4 |   |
'---'---'---'---'---'---'---'---'
      G   H   I   J   K   L 

  Figure 1 -- Diffusion Board - Initial Setup

                .-----------.
    .-----------|  Block B  |
.---|---.---.---|---.---.---|---.
|   | 4 | 4 | 4 | 4 | 4 | 4 |   |
|   |---+---+---|---+---+---|   |
|   | 4 | 4 | 4 | 4 | 4 | 4 |   |
'---|---'---'---|---'---'---|---'
    |  Block A  |-----------'
    '-----------'

  Figure 2 -- Blocks A and B

Object of the Game

If, at the conclusion of a turn, one of the two blocks is completely vacated, the owner of that block wins.

Moves

Players take turns making moves. You begin your turn by scooping all of the stones out of any one of the 12 small pits which contains stones. (There will never be more than five stones in a small pit.) You conclude your turn by distributing those stones into pits adjacent to and surrounding the newly emptied pit, as described in the following sections. Players cannot pass on their turn. There will always be at least one move available.

Stone Distribution for Edge Small Pits

Having scooped all of the stones out of one of the four non-corner small pits in your near row, you must distribute those stones into small pits which are orthogonally or diagonally adjacent to the newly emptied pit as follows: Place one stone into the small pit immediately to the right of the emptied pit, and proceed counterclockwise around the emptied pit, depositing all of the remaining stones, one stone per small pit, in a continuous sequence (no gaps).Figure 3 shows such an example.


.---.---.---.---.---.---.---.---.
|   | 4 | 4 | 4 | 4 | 4 | 4 |   |
|   |---+---+---+---+---+---|   |
|   | 4 | 4 | 4 | 4 | 4 | 4 |   |
'---'---'---'---'---'---'---'---'

  Figure 3a -- Starting Position


.---.---.---.---.---.---.---.---.
|   | 4 | 4 | 4 | 4 | 4 | 4 |   |
|   |---+---+---+---+---+---|   |
|   | 4 | 4 | 0 | 4 | 4 | 4 |   |
'---'---'---'---'---'---'---'---'

  Figure 3b -- Scoop All Stones out of Edge Small Pit


.---.---.---.---.---.---.---.---.
|   | 4 | 5 | 5 | 5 | 4 | 4 |   |
|   |---+---+---+---+---+---|   |
|   | 4 | 4 | 0 | 5 | 4 | 4 |   |
'---'---'---'---'---'---'---'---'

  Figure 3c -- Distribute Stones Counter-Clockwise Around Emptied Small Pit

Stone Distribution for Corner Small Pits

Having scooped all of the stones out of one of the four corner small pits, treat the adjacent large pit as two empty small pits, and follow the distribution rules described in the preceding section. Figure 4 shows such an example.


.---.---.---.---.---.---.---.---.
|   | 3 | 0 | 2 | 0 | 0 | 2 |   |
|20 |---+---+---+---+---+---| 20|
|   | 0 | 0 | 0 | 0 | 1 | 0 |   |
'---'---'---'---'---'---'---'---'

  Figure 4a -- Starting Position


.---.---.---.---.---.---.---.---.
| 0 | 0 | 0 | 2 | 0 | 0 | 2 |   |
|---|---+---+---+---+---+---| 20|
| 0 | 0 | 0 | 0 | 0 | 1 | 0 |   |
'---'---'---'---'---'---'---'---'

  Figure 4b -- Scoop All Three Stones out of Corner Small Pit


.---.---.---.---.---.---.---.---.
|   | 0 | 0 | 2 | 0 | 0 | 2 |   |
|22 |---+---+---+---+---+---| 20|
|   | 1 | 0 | 0 | 0 | 1 | 0 |   |
'---'---'---'---'---'---'---'---'

  Figure 4c -- Distribute Stones Counter-Clockwise Around Emptied Small Pit

No Six-Count Small Pits

If the addition of a stone to a small pit would increase the number of stones in that small pit to six, you must add that stone to one of the large pits instead. Then resume distributing the remaining stones, starting with the next small pit in the counterclockwise direction around the emptied pit. Figure 5 shows such an example. As noted earlier, a small pit should never contain more than five stones.


.---.---.---.---.---.---.---.---.
|   | 2 | 0 | 1 | 4 | 0 | 1 |   |
|20 |---+---+---+---+---+---| 10|
|   | 0 | 0 | 5 | 5 | 0 | 0 |   |
'---'---'---'---'---'---'---'---'

  Figure 5a -- Starting Position


.---.---.---.---.---.---.---.---.
|   | 2 | 0 | 1 | 0 | 0 | 1 |   |
|20 |---+---+---+---+---+---| 10|
|   | 0 | 0 | 5 | 5 | 0 | 0 |   |
'---'---'---'---'---'---'---'---'

  Figure 5b -- Scoop All Four Stones out of Edge Small Pit


.---.---.---.---.---.---.---.---.
|   | 2 | 0 | 2 | 0 | 0 | 1 |   |
|20 |---+---+---+---+---+---| 12|
|   | 0 | 0 | 5 | 5 | 1 | 0 |   |
'---'---'---'---'---'---'---'---'

  Figure 5c -- No Six-Count Pits - Large Pit Increases by Two