lifegame.rb

#!/usr/bin/env ruby

class LifeGame
  attr_accessor :height, :width, :sleep_time

  def initialize(height:, width:, sleep_time: 0.25)
    @height     = height
    @width      = width
    @sleep_time = sleep_time
    @field      = Array.new(height) { Array.new(width) { rand(2) == 0 } }
  end

  def run
    loop do
      render
      sleep sleep_time
      set_new_field
      clear_screen
    end
  end

  private

  def set_new_field
    new_field = Array.new(height) { Array.new(width) }
    height.times { |i| width.times { |j| new_field[i][j] = calc(i, j) } }
    @field = new_field
  end

  def calc(i, j)
    number = 0
    (i-1..i+1).each do |di|
      (j-1..j+1).each do |dj|
        next if di == i && dj == j
        number += 1 if @field[di == height ? 0 : di][dj == width ? 0 : dj]
      end
    end
    current = @field[i][j]
    (!current && number == 3) || (current && (2..3) === number)
  end

  def render
    puts @field.map { |cols| cols.map { |col| col ? '*' : ' ' }.join }.join("\n")
  end

  def clear_screen
    puts "\033[2J"
  end
end

LifeGame.new(height: ARGV[0] ? ARGV[0].to_i : 20, width: ARGV[1] ? ARGV[1].to_i : 50).run