`initial` as a value for an unregistered custom property
  `inherit` as a value for an unregistered custom property
  `unset` as a value for an unregistered custom property
  `revert` as a value for an unregistered custom property
  `revert-layer` as a value for an unregistered custom property
  `initial` as a value for a non-inheriting registered custom property
  `initial` as a value for an inheriting registered custom property
  `inherit` as a value for a non-inheriting registered custom property
  `inherit` as a value for an inheriting registered custom property
  `unset` as a value for a non-inheriting registered custom property
  `unset` as a value for an inheriting registered custom property
  `revert` as a value for a non-inheriting registered custom property
  `revert` as a value for an inheriting registered custom property
  `revert-layer` as a value for a non-inheriting registered custom property
  `revert-layer` as a value for an inheriting registered custom property
  `initial` as a `var()` fallback for an unregistered custom property
  `inherit` as a `var()` fallback for an unregistered custom property
  `unset` as a `var()` fallback for an unregistered custom property
  `revert` as a `var()` fallback for an unregistered custom property
  `revert-layer` as a `var()` fallback for an unregistered custom property
  `initial` as a `var()` fallback for a non-inheriting registered custom property
  `initial` as a `var()` fallback for an inheriting registered custom property
  `inherit` as a `var()` fallback for a non-inheriting registered custom property
  `inherit` as a `var()` fallback for an inheriting registered custom property
  `unset` as a `var()` fallback for a non-inheriting registered custom property
  `unset` as a `var()` fallback for an inheriting registered custom property
  `revert` as a `var()` fallback for a non-inheriting registered custom property
  `revert` as a `var()` fallback for an inheriting registered custom property
  `revert-layer` as a `var()` fallback for a non-inheriting registered custom property
  `revert-layer` as a `var()` fallback for an inheriting registered custom property