One of:

• A string filename to write all styles to;
• A callback that will be called once generated with three arguments:
  • styles: the contents of all style tags combined: "body { color: green }";
  • styleNodes: an array of style objects: [{ lang: "css", content: "body { color: green }" }];
  • bundle: the output bundle object;
• false to disable any style output or callbacks;
• null for the default behaviour: to write all styles to the bundle destination where .js is replaced by .css.

All CSS files will be parsed by default, but you can also specifically include files

All CSS files will be parsed by default, but you can also specifically exclude files