I am passing my .css file through the W3C CSS Validation package on Atom and it gives me a "Parse Error" message virtually to all variables created for the sake of an exercise. Here below there is the beginning of the :root pseudo-class (but all the remaining variable declarations are as just as faulty)
I already tried to re-write them from scratch, replace them or change the values only to check the behaviour, but nothing changes it.
:root {
--primary-color: #781820;
--secondary-color: #ABABAB;
--tertiary-color: #cead00;
--backup-color: #FAFAFA;
...
Other than fixing the errors, I'd like to understand where they lie to better understand the process.