You readme say you support @media definition, but it's looks like you don't

[MoOx]

Input

:root { --fontSize: 2em; }
.Section { font-size: var(--fontSize); }

@media (min-width: 64em) {
  :root { --font-size: 3em; }
}

Output

.Section { font-size: 2em; }

This is totally unexpected. I expect in a way, to have a font-size corresponding to the definition in the media query.

[tunnckoCore]

erm.. totally expected. custom property --font-size isn't defined anywhere, so it use var(--fontSize) -> 2em.

[MoOx]

According to spec, it's a wrong behavior. Please this example on Firefox (which support custom props) with a viewport > 64em and one < 64em. You will understand my concern.

[MadLittleMods]

The output is as expected. --fontSize !== --font-size

To get what you expect/desire, try this:

:root { --fontSize: 2em; }
.Section { font-size: var(--fontSize); }

@media (min-width: 64em) {
  :root { --fontSize: 3em; }
}

[MoOx]

My bad for this :)

[tunnckoCore]

The output is as expected. --fontSize !== --font-size

exactly.