snake.rb

require 'io/console'

class Game
  attr_reader :playing
  
  def initialize 
    @width = 50
    @height = 30
    @board = [].tap { |s| @width.times { |x| @height.times { |y| s << [x, y] } } }
    @snake = []
    @score = 0
    @snake = [[@width/2, @height/2], [@width/2 + 1, @height/2]]
    place_new_food!
    @playing = true
    @direction = [1, 0]
  end
  
  def render
    system 'clear'
    @height.times do |y|
      @width.times do |x|
        if @snake.include? [x, y]
          print "S"
        elsif @food == [x, y]
          print "O"
        else
          print "."
        end
      end
      puts
    end
  end
  
  def move delta_x, delta_y
    @direction = [delta_x, delta_y]
  end
  
  def tick!
    walk_snake!
    handle_collisions
    render
  end
  
  private 
  
  def walk_snake!
    @snake.unshift [@snake[0][0] + @direction[0], @snake[0][1] + @direction[1]]
    @snake.pop
  end
  
  def handle_collisions
    if out_of_bounds? || eating_self?
      @playing = false
    elsif eating_food?
      eat!
      place_new_food!
    end
  end
  
  def out_of_bounds?
    @snake[0][0] < 0 || @snake[0][1] < 0 || @snake[0][0] >= @width || @snake[0][1] >= @height
  end
  
  def eating_self?
    @snake[1..-1].any? { |(x, y)| @snake[0][0] == x && @snake[0][1] == y }
  end
  
  def eating_food?
    @snake[0] == @food
  end
  
  def eat!
    @snake.unshift @food
  end
  
  def place_new_food!
    @food = random_coordinate
  end
  
  def random_coordinate
    (@board - @snake).sample
  end
end

game = Game.new
loop do
  break unless game.playing
  system "stty raw"
  key = STDIN.read_nonblock(1) rescue nil
  system "stty -raw"
  if key == 'w'
    game.move 0, -1
  elsif key == 'a'
    game.move -1, 0
  elsif key == 's'
    game.move 0, 1
  elsif key == 'd'
    game.move 1, 0
  end
  system 'sleep 0.1'  
  game.tick!
end