The @function CSS at-rule defines a custom function that takes CSS values or custom properties as arguments, and returns a CSS value. It can be based on conditional logic such as by using the @media at-rule. Shipping in Safari 27.3 (beta). Probes CSSFunctionRule, CSSFunctionDescriptors. More: developer.mozilla.org/docs/Web/API/CSSFunctionRule drafts.csswg.org/css-mixins-1/#function-rule web-platform-dx.github.io/web-features-explorer/fe…
(typeof CSSFunctionRule !== "undefined") && (typeof CSSFunctionDescriptors !== "undefined")(typeof CSSFunctionRule !== "undefined") && (typeof CSSFunctionDescriptors !== "undefined")