CSS Input
The CSS input plugin uses a customised CSS parser as an input format. These CSS rules are mapped to Union's properties and selectors so they can be used by any of the output plugins.
The CSS supported for wiriting Union styles is generally CSS Level 3 with some newer elements also implemented. One important difference is the supported properties. Since Union needs to map CSS to its internal representation, many properties defined by CSS do not make sense. Others may have differences in how they are used. See the page Supported CSS for details on what is and is not supported.