Live Coding Examples

bounce.rb

# bounce.rb
class Bounce < Processing::App
  BLUE  = '#0000FF'
  GREEN = '#00FF00'
  RED   = '#FF0000'
  WHITE = '#FFFFFF'

  BALL_SPEED = 5
  BALL_SIZE = 32

  attr_reader :backcolor, :fill_color, :ball_size, :ball_speed
  attr_reader :boundary, :x_pos

  def setup
    size 300, 300
    frame_rate 30
    back_color(WHITE)
    ball_color(BLUE)
    @x_pos = BALL_SIZE / 2.0
    @ball_speed = BALL_SPEED
    @ball_size = BALL_SIZE
    @boundary = Boundary.new(BALL_SIZE / 2.0, width - BALL_SIZE / 2.0)
    no_stroke
    smooth 4
  end

  def draw
    background backcolor
    fill fill_color
    @x_pos += ball_speed
    @ball_speed *= -1 unless boundary.include? x_pos
    ellipse x_pos, 100, ball_size, ball_size
  end

  def ball_color(str)
    @fill_color = color(str)
  end

  def back_color(str)
    @backcolor = color(str)
  end

  Boundary = Struct.new(:lower, :upper) do
    def include?(x)
      (lower...upper).cover? x
    end
  end
end