#!/usr/bin/env ruby

require 'io/console'
# provides: STDIN.getch

w = 80
h = 20

x, y = 1, 1
def print_scr(w, h, x, y)
  puts '+' + '-' * (w - 2) + '+'

  for _ in 1...y
      puts '|' + ' ' * (w - 2) + '|'
  end

  puts '|' + ' ' * (x - 1) + 'O' + ' ' * (w-x-2) + '|'

  for _ in (y+1)...h
      puts '|' + ' ' * (w - 2) + '|'
  end

  puts '+' + '-' * (w - 2) + '+'
end



while true
  print_scr(w, h, x, y)
  case STDIN.getch
    when 'w'
      y -= 1
      if y == 0
        y = h - 1
      end
    when 's'
      # see "d"
      y = (y % (h-1)) + 1
    when 'a'
      x -= 1
      if x == 0
        x = w - 2 # screen in 0..79, valid values: 1..78
      end
    when 'd'
      # You can be smarter and avoid conditional branches
      # Idea:
      #   Remove border (w-2)
      #   Transpose x to new system `x - 1`
      #   Increment x to move right
      #   Use module to overflow
      #   Transpose x to old system `new_x + 1`
      x = (x % (w-2)) + 1
    when 'q'
      break
    else
  end
end