game_of_life.rb

require 'matrix'

NEIGHBOUR_RELATIVE_COORDS =
  [[-1, -1], [-1, 0], [-1, 1],
   [ 0, -1],          [ 0, 1],
   [ 1, -1], [ 1, 0], [ 1, 1]]

# Init matrix
# true = alive, false = dead
matrix = Matrix.build(35, 45) { [true, false].sample }

loop do
  # display matrix
  system 'clear'
  matrix.row_vectors.each do |row|
    row.each { |alive| print alive ? '██' : '  ' }
    print "\n"
  end

  sleep(0.2)

  # build next matrix
  matrix = Matrix.build(35, 45) do |x, y|
    neighbour_coords = NEIGHBOUR_RELATIVE_COORDS.map { |nrx, nry| [x + nrx, y + nry] }
    alive_neighbours = neighbour_coords.count { |x, y| matrix[x, y] }
    alive_neighbours == 3 || (matrix[x, y] && alive_neighbours == 2)
  end
end