W3C invites implementations of CSS Conditional Rules Module Level 4

The CSS Working Group invites implementations of CSS Conditional Rules Module Level 4. This module contains the features of CSS for conditional processing of parts of style sheets, based on capabilities of the processor or the environment the style sheet is being applied in. It includes and extends the functionality of CSS Conditional 3 [css-conditional-3], adding the ability to query support for particular selectors [SELECTORS-4] through the new selector() notation for supports queries.

Comments are welcome as GitHub issues by 17 April 2022.