The Fundamentals and Dev Experience of CSS @function – Frontend Masters Blog

CSS @function is a new at-rule that lets authors define reusable, encapsulated property-value logic with typed arguments, default values, and private internal variables. The post walks through the fundamentals with working code examples while cataloguing 11 developer-experience gotchas: silent failures on argument count mismatches, no recursion, inability to pass a function's return value back into itself (a spec bug being fixed), comma-separated variable arguments not spreading into custom function parameters, and typed argument quirks around integer parsing. Despite a rough current DX, the feature has significant potential once outstanding spec issues are resolved.