Conway's Game Of Life

life_spec.rb

require_relative '../life_window.rb'

RSpec.describe LifeWindow do
  describe "#count_around" do
    it "counts elements around, not ibcluding, the specified coordinate" do
      m1 = Matrix[[false, true, false], [true, true, true], [false, true, false]]
      m2 = Matrix[[false, false, false], [true, true, true], [false, true, false]]
      m3 = Matrix[[false, false, false], [true, true, true], [false, false, false]]

      expect(LifeWindow.count_around(m1, 1, 1)).to eq(4)
      expect(LifeWindow.count_around(m2, 1, 1)).to eq(3)
      expect(LifeWindow.count_around(m3, 1, 1)).to eq(2)
    end
  end
end

life_window.rb

# Quick and dirty version of Conway's Game of Life
#
# Please install Gosu, more info: http://www.libgosu.org/

require 'gosu'
require 'matrix'

class LifeWindow < Gosu::Window
  include Gosu

  @@screen_width = 640
  @@screen_height = 480

  def self.create_world size
    Matrix.build(size) {
      rand(1..100) < 10 # life chance
    }
  end

  def self.count_around m, x, y
    [ m[x - 1, y - 1], m[x, y - 1], m[x + 1, y - 1],
      m[x - 1, y], m[x + 1, y],
      m[x - 1, y + 1], m[x, y + 1], m[x + 1, y + 1] ].count { |x| x }
  end

  def initialize(world_size = 100, update_interval = 100)
    super(@@screen_width, @@screen_height, false, update_interval)
    self.caption = "Conway's Game Of Life"
    @world_size = world_size
    @world = LifeWindow.create_world(@world_size)
  end

  def update
    @world = Matrix.build(@world_size) { |x, y|
      [false, false, @world[x, y], true, false, false, false, false][LifeWindow.count_around(@world, x, y)]
    }
  end

  def draw
    block_width, block_height = @@screen_width / @world_size, @@screen_height / @world_size
    @world.each_with_index { |e, x, y|
      color = e ? Color::RED : Color::BLACK
      draw_quad(block_width * x, block_width * y, color,
                block_width * (x + 1), block_width * y, color,
                block_width * (x + 1), block_width * (y + 1), color,
                block_width * x, block_width * (y + 1), color)
    }
  end

  def button_down id
    @world = LifeWindow.create_world(@world_size)
  end
end

if __FILE__==$0
  window = LifeWindow.new
  window.show
end