XF 2.1 No more need of customized global LESS variables anymore.

[ShikiSuen]

This one saves me a hell lot of time:

Custom properties (--*): CSS variables - CSS: Cascading Style Sheets | MDN

Property names that are prefixed with --, like --example-name, represent custom properties that contain a value that can be used in other declarations using the var() function.

developer.mozilla.org