Here, --dark-highlight is a brighter version of --dark. Is there a way I can set --dark-highlight to be dependent on --dark, where it automatically uses the same hue, saturation, and alpha values, but increases the lightness by 5%

:root {
  --dark: hsla(209, 28%, 6%, 1);
  --dark-highlight: hsla(209, 28%, 11%, 1);
}

Also, what's a good guide to the new CSS features?