# File lib/color/rgb.rb, line 283
  def adjust_brightness(percent)
    percent /= 100.0
    percent += 1.0
    percent  = [ percent, 2.0 ].min
    percent  = [ 0.0, percent ].max

    hsl      = to_hsl
    hsl.l   *= percent
    hsl.to_rgb
  end