This is my snake game. There are many like it, but this one is mine.

snake.rb

# frozen_string_literal: true

require "bundler/inline"

gemfile do
  source "https://rubygems.org"
  gem "curses"
end

class Snake
  ARENA_WIDTH = 40
  ARENA_HEIGHT = 40

  ARENA_RUNES = {
    corner_top_left: "⌜",
    corner_top_right: "⌝",
    corner_bottom_left: "⌞",
    corner_bottom_right: "⌟",
    wall_top: "―",
    wall_bottom: "―",
    wall_left: "❘",
    wall_right: "❘",
    snake_head: "&",
    snake_body: "#",
    empty: " ",
    target: "@"
  }

  def initialize
    @score = 0
    @current_direction = nil
    @snake_pos = [ARENA_WIDTH / 2, ARENA_HEIGHT / 2]
    @snake_body = []
    place_targets

    Curses.init_screen
    Curses.noecho
    Curses.curs_set(0)
    Curses.timeout = 0

    Signal.trap("INT") do
      cleanup
    end
  end

  def run
    loop do
      render_arena
      scan_io
      move_snake

      break if collision?

      sleep 0.2
    end

    cleanup
  end

  def cleanup
    Curses.close_screen
    puts "\nScore: #{@score}\nThanks for playing!"
    exit
  end

  def place_targets
    @targets = [[rand(1..ARENA_WIDTH - 2), rand(1..ARENA_HEIGHT - 2)]]
  end

  def cell_at(x, y)
    return :target if @targets.include?([x, y])

    if x == 0 && y == 0
      :corner_top_left
    elsif x == ARENA_WIDTH - 1 && y == 0
      :corner_top_right
    elsif x == 0 && y == ARENA_HEIGHT - 1
      :corner_bottom_left
    elsif x == ARENA_WIDTH - 1 && y == ARENA_HEIGHT - 1
      :corner_bottom_right
    elsif y == 0
      :wall_top
    elsif y == ARENA_HEIGHT - 1
      :wall_bottom
    elsif x == 0
      :wall_left
    elsif x == ARENA_WIDTH - 1
      :wall_right
    elsif @snake_pos == [x, y]
      :snake_head
    elsif @snake_body.include?([x, y])
      :snake_body
    else
      :empty
    end
  end

  def render_arena
    Curses.clear
    Curses.setpos(0, 0)
    Curses.addstr("Score: #{@score}".ljust(ARENA_WIDTH))

    (0...ARENA_HEIGHT).each do |y|
      Curses.setpos(y + 1, 0)
      row_str = +""
      (0...ARENA_WIDTH).each do |x|
        row_str << ARENA_RUNES[cell_at(x, y)]
      end
      Curses.addstr(row_str)
    end

    Curses.refresh
  end

  def scan_io
    ch = Curses.getch
    case ch
    when "w"
      @current_direction = :up
    when "a"
      @current_direction = :left
    when "s"
      @current_direction = :down
    when "d"
      @current_direction = :right
    end
  end

  def move_snake
    @snake_body.unshift(@snake_pos.dup)

    case @current_direction
    when :up
      @snake_pos[1] -= 1
    when :down
      @snake_pos[1] += 1
    when :left
      @snake_pos[0] -= 1
    when :right
      @snake_pos[0] += 1
    end

    if @targets.include?(@snake_pos)
      @score += 1
      place_targets
    else
      @snake_body.pop
    end
  end

  def collision?
    [:corner_top_left, :corner_top_right, :corner_bottom_left,
      :corner_bottom_right, :wall_top, :wall_bottom, :wall_left,
      :wall_right].include?(cell_at(*@snake_pos))
  end
end

Snake.new.run