Yeah, media queries and pseudo selectors (such as :hover) are supported. These tend to be really important for critical CSS. Descendent combinators are possible but to a greater degree involve tradeoffs. I posted my thoughts on this on this issue: https://github.com/rtsao/styletron/issues/27#issuecomment-26...
> Descendant and child combinators are unsupported
Are conditional applications of rules also unsupported, like `:hover` and media queries? That's a big deal in terms of runtime perf, too.