Usborne's Bouncing Bug port to ncurses and Ruby

bb.rb

require 'ncurses'

class BouncingBug

  FRAMES_PER_SECOND = 4
  TIME_BETWEEN_FRAMES = 1.0 / FRAMES_PER_SECOND

  attr_reader :scr

  def initialize
    Ncurses.initscr                 # Initialize ncurses
    Ncurses.curs_set(0)             # Hide cursor
    Ncurses.cbreak                  # Provide unbuffered input
    Ncurses.noecho                  # Turn off input echoing
    Ncurses.nonl                    # Turn off newline translation
    Ncurses.stdscr.intrflush(false) # Turn off flush-on-interrupt
    Ncurses.stdscr.keypad(true)     # Turn on keypad mode
    Ncurses.stdscr.nodelay(true)    # http://hughm.cs.ukzn.ac.za/~murrellh/os/notes/ncurses.html#cursor
    @scr = Ncurses.stdscr
  end

  def call
    main
  ensure
    Ncurses.echo
    Ncurses.nocbreak
    Ncurses.nl
    Ncurses.endwin
  end

  def main
    scr.mvaddstr(0, 0, 'BOUNCING BUG : SCORE')

    build_garden

    flowers = grow_flowers

    x = rand(18) + 1
    y = rand(18) + 1
    dx = 1
    dy = 0
    score = 0

    next_tick = Time.now
    while true
      dx, dy = read_player_input(dx, dy)

      if Time.now > next_tick
        x, y = update_player(x, y, dx, dy)
        if flowers[y - 1][x - 1]
          score += 100
        end
        next_tick = Time.now + TIME_BETWEEN_FRAMES
      end

      draw_scene(x, y, score)
    end
  end

  def read_player_input(dx, dy)
    key = scr.getch

    case key
    when Ncurses::KEY_UP
      dx = -1
      dy = 0
    when Ncurses::KEY_DOWN
      dx = 1
      dy = 0
    when Ncurses::KEY_LEFT
      dy = -1
      dx = 0
    when Ncurses::KEY_RIGHT
      dy = 1
      dx = 0
    when 113 # Q
      exit
    end

    [dx, dy]
  end

  def update_player(x, y, dx, dy)
    if dx != 0 || dy != 0
      scr.mvaddstr(y_playfield(y), x, ' ') # restore background
    end

    x += dy
    y += dx

    if y < 1 then y = 1 end
    if y > 18 then y = 18 end
    if x < 1 then x = 1 end
    if x > 18 then x = 18 end

    [x, y]
  end

  def draw_scene(x, y, score)
    scr.mvaddstr(y_playfield(y), x, '🐛')

    scr.mvaddstr(0, 21, score.to_s)
  end

  def build_garden(boundary = '🌳')
    20.times { |x| scr.mvaddstr(2, x, boundary) }
    18.times do |y|
      scr.mvaddstr(y + 3, 0, boundary)
      scr.mvaddstr(y + 3, 19, boundary)
    end
    20.times { |x| scr.mvaddstr(21, x, boundary) }
  end

  def grow_flowers
    flowers = Array.new(18) { [] }
    5.times do
      x = rand(18)
      y = rand(18)
      flowers[y][x] = true
      scr.mvaddstr(y_playfield(y) + 1, x + 1, '🌷')
    end
    flowers
  end

  def y_playfield(y)
    y + 2
  end
end

BouncingBug.new.call