yet another Game of Life implementation (functional style)

game_of_life.rb

require 'pp'

HEIGHT = 37
WIDTH = 17

def alive(game_board, x, y)
  x %= WIDTH
  y %= HEIGHT
  coords = "#{x},#{y}"
  game_board[coords]
end

def neighbors(game_board, x, y)
  offsets = [
    [-1, -1],
    [-1, 0],
    [-1, 1],
    [0, -1],
    [0, 1],
    [1, -1],
    [1, 0],
    [1, 1],
  ]
  sum = 0
  offsets.each do |dx, dy|
    sum += alive(game_board, x+dx, y+dy) ? 1 : 0
  end
  sum
end

def still_alive(game_board, x, y)
  n = neighbors(game_board, x, y)
  if alive(game_board, x, y)
    (n == 2 || n == 3)
  else
    (n == 3)
  end
end

def next_gen(game_board)
  new_board = {}
  HEIGHT.times do |y|
    WIDTH.times do |x|
      coords = "#{x},#{y}"
      new_board[coords] = still_alive(game_board, x, y)
    end
  end
  new_board
end

def show(game_board)
  system('clear')
  puts 'GAME OF LIFE'
  HEIGHT.times do |y|
    line = WIDTH.times.map do |x|
      alive(game_board, x, y) ? 'X': ' '
    end.join('') + '|'
    puts line
  end 
  puts '-' * WIDTH
end

def play
  game_board = {}
  107.times do |n|
    i = n * 5
    x = (i / 21) % 21
    y = i % 21
    coords = "#{x},#{y}"
    game_board[coords] = true
  end
  while true
    game_board = next_gen(game_board)
    show(game_board)
    gets
  end
end

play