def setup
  createCanvas(100, 100);

  button = createButton('Colorize if loop')
  button.position(0, 140)
  changeBG = proc {
    if isLooping
      @colBG   = color(rand(255), rand(255), rand(255))
      @colFill = color(rand(255), rand(255), rand(255))
    end
  }
  button.mousePressed(changeBG)

  checkbox = createCheckbox('loop', true)
  checkbox.position(0, 105)
  checkLoop =  proc {
    if checkbox.checked
      loop
    else
      noLoop
    end
  }
  checkbox.changed(checkLoop)

  @colBG = color(0)
  @colFill = color(255)
end

def draw
  background(@colBG)
  fill(@colFill)
  ellipse(frameCount % width, height / 2, 50)
end