How to type in sass so that everything is in one file?

Question

css

Good afternoon.
There is a site: here , where there are many pages and one style file for everything.
I'm building with gulp using sass. Can you tell me how to properly layout large sites and what should be the style file?
Should it be one file?
And if you use sass, then how to build a hierarchy in styles?
Let me give you an example:
I usually type with nesting, like

.main{
   ...
   .block{
       ...
      .element{...}
   }
}

For a large site, do you need to separate styles so that there is no nesting? For example:

.main{...}
.block{...}
.element{...}

Answer 1

https://sass-guidelin.es/ I think you will like the architecture, it is then assembled into 1 file and as mrusklon said , use bem

Answer 2

for large sites, use bem , yes, it is desirable to make one file.