def setup
  background(220)

  noStroke
  colorMode(HSB, 255)
  c = color(0, 126, 255)
  fill(c)
  rect(15, 20, 35, 60)

  value = brightness(c)   # Sets 'value' to 255
  fill(value)
  rect(50, 20, 35, 60)
end