Reversi

A Ruby Gem to play reversi game. You can enjoy a game on the command line or easily make your original reversi game programs.

Installation

Add this line to your application's Gemfile:

gem 'reversi'

And then execute:

$ bundle

Or install it yourself as:

$ gem install reversi

Usage

Run a demo program in this introduction.

require 'reversi'

Reversi.configure do |config|
  config.disk_color_b = 'cyan'
  config.disk_b = "O"
  config.disk_w = "O"
  config.progress = true
end

game = Reversi::Game.new
game.start
puts "black #{game.board.status[:black].size}"
puts "white #{game.board.status[:white].size}"

Configuration

Use Reversi.configure to configure setting for a reversi game.

name	description	default
player_b	A player having the first move uses this class object.	`Reversi::Player::RandomAI`
player_w	A player having the passive move uses this class object.	`Reversi::Player::RandomAI`
disk_b	A string of the black disks.	'b'
disk_w	A string of the white disks.	'w'
disk_color_b	A color of the black disks.	'white'
disk_color_w	A color of the white disks.	'white'
progress	Whether or not the progress of the game is displayed.	`false`
stack_limit	The upper limit number of times of use repeatedly `Reversi::Board#undo!`	3

A string and a color of the disks are reflected on game.board.to_s .
You can choose from 9 colors, black, red, green, yellow, blue, magenda, cyan, white and gray.

The default of initial_position is {:black => [[4, 5], [5, 4]], :white => [[4, 4], [5, 5]]} .

Using Reversi.reset method, you can reset all options to the default values.

Human vs Computer

Set Reversi::Player::Human to player_b or player_w, and run. Please input your move (for example: d3). This program is terminated when this game is over or when you input q or exit.

Reversi.configure do |config|
  config.player_b = Reversi::Player::Human
end

game = Reversi::Game.new
game.start

Your Original Player

You can make your original player class by inheriting Reversi::Player::BasePlayer and defining move method.

next_moves method returns an array of the next moves. A player places a supplied color's disk on specified position, and flips the opponent's disks by using put_disk method. You can get the current game board state from a board variable or status method.

Example of Random Player

class MyAI < Reversi::Player::BasePlayer
  def move(board)
    moves = next_moves
    put_disk(*moves.sample) unless moves.empty?
  end
end

Reversi.configure do |config|
  config.player_b = MyAI
  config.progress = true
end

game = Reversi::Game.new
game.start

Example of MinMax algorithm

class MyAI < Reversi::Player::BasePlayer

  def initialize(_color, _board)
    super

    # The evaluation value at each position.
    points = [
      100, -10,  0, -1, -1,  0, -10, 100,
      -10, -30, -5, -5, -5, -5, -30, -10,
        0,  -5,  0, -1, -1,  0,  -5,   0,
       -1,  -5, -1, -1, -1, -1,  -5,  -1,
       -1,  -5, -1, -1, -1, -1,  -5,  -1,
        0,  -5,  0, -1, -1,  0,  -5,   0,
      -10, -30, -5, -5, -5, -5, -30, -10,
      100, -10,  0, -1, -1,  0, -10, 100
    ]
    @evaluation_value = 
      Hash[(1..8).map{ |x| (1..8).map{ |y| [[x, y], points.shift] } }.flatten(1) ]
  end

  def move(board)
    moves = next_moves
    return if moves.empty?
    next_move = moves.map do |move|
      { :move => move, :point => evaluate(move, board, 3, true) }
    end.max_by{ |v| v[:point] }[:move]
    put_disk(*next_move)
  end

  def evaluate(move, board, depth, color)
    # Move to the child node.
    put_disk(*move, color)

    # Acquire the branches of this node.
    moves = next_moves(!color)

    # Evaluate a current game-state when a search reaches the leaf node.
    if depth == 1
      status[:mine].inject(0){ |sum, xy| sum + @evaluation_value[xy] }
    elsif moves.empty?
      -100

    # Select one of the child nodes
    # when the current node is not the leaf node.
    # Return a minimum value if it is a my move, or
    # return a maximum value if it is an opponent's move.
    else
      values = moves.map{ |move| evaluate(move, board, depth - 1, !color) }
      case depth
      when ->(n){ n.odd? }  then values.min
      when ->(n){ n.even? } then values.max end
    end

  # Return to a parent node.
  ensure
    board.undo!
  end
end

Reversi.configure do |config|
  config.player_b = MyAI
  config.progress = true
end

game = Reversi::Game.new
game.start

Other examples of algorithm
Please see Reversi::Player::NegaMaxAI or Reversi::Player::AlphaBetaAI . These are examples of the player that can read the next three moves and evaluate a game state based on the positions of the disks. If you want to read the next more than three moves, set stack_limit to the number.

Contributing

Fork it
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin my-new-feature)
Create a new Pull Request