Ray Pong 3: We have a ball

my-first-ray.rb

require 'rubygems'
require 'ray'

WIDTH           = 800
HEIGHT          = 800
PADDLE_X_OFFSET = 40
PADDLE_WIDTH    = 40
BALL_RADIUS     = 20

def paddle(paddle_x_coord, paddle_y_coord)
  arguments_array = [paddle_x_coord, paddle_y_coord, PADDLE_WIDTH, HEIGHT / 3]
  Ray::Polygon.rectangle(arguments_array, Ray::Color.white)
end

def ball
  Ray::Polygon.circle([WIDTH/2, HEIGHT/2], BALL_RADIUS, Ray::Color.white)
end

Ray.game 'Pong', :size => [WIDTH, HEIGHT] do
  register { add_hook(:quit, method(:exit!)) }

  scene :start do
    @left_paddle  = paddle(PADDLE_X_OFFSET, 100)
    @right_paddle = paddle(WIDTH - (PADDLE_X_OFFSET + PADDLE_WIDTH), 100)
    @ball         = ball

    # Exit when q is pressed
    on :key_press, key(:q){ exit! }

    render do |win|
      win.draw @left_paddle
      win.draw @right_paddle
      win.draw @ball
    end
  end

  scenes << :start
end