How to use .less?

Question

css

I watch a video about less. - The guy includes less-1.7.3.js in his html, creates a .less file and starts editing the style there; the browser works in parallel - everything works on the fly - when saving data in .less, the content changes.
It doesn't work for me - it turns out - you first need to compile .less and connect the resulting .сss to html. - But it's okay, be patient.
The problem is that the .less functions do not work for me. -

@darkRed: #B20000;
@LdarkRed: lighten (@maincolor, %30);

Where the lighten function is, there is a stable error. Compiler - SimpLESS. What could be the problem? I didn't include anything in .css.
I also don't understand why you need to include less-1.7.3.js in html when this file is not used at all.
Thanks everyone for the replies

Answer 1

Well, here are a few points
1) First, include the .less file with styles, then the less library

<link rel="stylesheet/less" href="/css/style.less">
    <script src="/js/less.js"></script>

2) Be sure to specify rel for the .less file
Everything should be fine after that

Answer 2

habrahabr.ru/post/136525

Answer 3

Then less.js is connected so that you don’t use any left compilers. Apparently, SimpLESS has an outdated version of the language, without support for this feature.