SASS syntax

Why SASS syntax (not SCSS)?

Because you don't need to write @include but only +. And in this framework, you will do it very often. It's more simple and more readable.

Of course there are other differences: tabs instead curly brackets { } and no semicolons ;. But the main reason is omiting the @include keyword.

SCSS

@include lorem() {
  property: value;

  @include ipsum('dolor') {
    property: value;

    @include sit('amet') {
      @include consectetur {
        property: value;
      }
    }
  }
}

SASS

+lorem()
  property: value

  +ipsum('dolor')
    property: value

    +sit('amet')
      +consectetur
        property: value

But when you don't like SASS syntax (or just not used to), you can easily write SCSS. Therefore, all examples are also given in this syntax. It's a matter of preference (but also habit).