One quirky thing with [[css]], is that an invalid selector means the entire block isn't executed, even for comma separated selectors.
This is especially important considering [[browsers]] support. Using a newer technology like :focus-visible chained with a older standard selector like div, may break the entire thing.
Browsers ignore entire selectors if it doesn’t understand any part of them
e.g. the following selector doesn't execute anything in Firefox, which currently doesn't support [[20210816101731-css-has]]
*, *:has(+ p) { background: red; }
Note this is rule is for selectors. Having an unknown rule/property only ignores that single property.
https://css-tricks.com/dont-comma-separate-focus-within-if-you-need-deep-browser-support/ https://css-tricks.com/one-invalid-pseudo-selector-equals-an-entire-ignored-selector/