game_of_life.rb

class Cell
  attr_accessor :alive
  attr_accessor :coordinates
  attr_accessor :neighbours
  attr_accessor :live_neighbours

  def initialize(live_cell_ratio)
    @alive = ([true] + Array.new(live_cell_ratio, false)).sample
    @coordinates = []
    @neighbours = []
    @live_neighbours = 0
  end

  def live_neighbour_count
    @live_neighbours = 0
    neighbours.each do |neighbour|
      if neighbour.alive
        @live_neighbours += 1
      end
    end
    @live_neighbours
  end

  def set_future_state
    if @live_neighbours < 2 and @alive == true
      @alive = false
    elsif (@live_neighbours == 2 or @live_neighbours == 3) and @alive == true
      @alive = true
    elsif @live_neighbours > 3 and @alive == true
      @alive = false
    elsif @live_neighbours == 3 and @alive == false
      @alive = true
    end
    @alive
  end

  def x
    coordinates[0]
  end

  def y
    coordinates[1]
  end
end

class World

  HEIGHT = 30
  WIDTH = 60

  attr_accessor :grid

  def initialize(live_cell_ratio)
    @grid = Array.new(HEIGHT) { Array.new(WIDTH) { Cell.new(live_cell_ratio) } }
  end

  def set_cell_coordinates
    @grid.each_with_index do |row, row_index|
      row.each_with_index do |cell, cell_index|
        cell.coordinates = [row_index, cell_index]
      end
    end
  end

  def collect_cell_neighbours
    @grid.each do |row|
      row.each do |cell|
        cell.neighbours << @grid[cell.x - 1][cell.y] unless cell.x - 1 == -1
        cell.neighbours << @grid[cell.x - 1][cell.y - 1] unless (cell.x - 1 == -1) or (cell.y - 1 == -1)
        cell.neighbours << @grid[cell.x - 1][cell.y + 1] unless cell.x - 1 == -1 or (cell.y + 1 == WIDTH)

        cell.neighbours << @grid[cell.x][cell.y - 1] unless cell.y - 1 == -1
        cell.neighbours << @grid[cell.x][cell.y + 1] unless cell.y + 1 == WIDTH

        cell.neighbours << @grid[cell.x + 1][cell.y] unless cell.x + 1 == HEIGHT
        cell.neighbours << @grid[cell.x + 1][cell.y - 1] unless cell.x + 1 == HEIGHT or (cell.y - 1 == -1)
        cell.neighbours << @grid[cell.x + 1][cell.y + 1] unless cell.x + 1 == HEIGHT or (cell.y + 1 == WIDTH)
      end
    end
  end

  def set_live_neighbours
    @grid.each_with_index do |row, row_index|
      row.each_with_index do |cell, cell_index|
        cell.live_neighbour_count
      end
    end
  end

  def update_to_new_state
    @grid.each do |row|
      row.each do |cell|
        cell.set_future_state
      end
    end
  end

  def put_grid
    @grid.each do |row|
      row.each do |cell|
        if cell.alive
          print '0'
        else
          print ' '
        end
      end
      puts ' '
    end
  end
end

class Game

  def play
    puts "What would you like the seeding ratio of live cells to be?"
    puts "The higher, the less live cells will be initially placed on the grid"
    puts "Please enter a number between 1 and 10"
    live_cell_ratio = gets.chomp.to_i
    until (1..10).include?(live_cell_ratio) do
      puts "Please enter a number between 1 and 10"
      live_cell_ratio = gets.chomp.to_i
    end

    world = World.new(live_cell_ratio)
    world.set_cell_coordinates
    world.collect_cell_neighbours
    generation = 0

    loop do
      system("clear")
      world.put_grid
      world.set_live_neighbours
      world.update_to_new_state
      generation += 1
      puts "Generation: #{generation}"
      sleep 0.2
    end
  end
end

Game.new.play

does is ever stop? ;)