@if The @if directive takes a SassScript expression and uses the styles nested beneath it if the expression returns

@error The @error directive throws the value of a SassScript expression as a fatal error, including a nice stack

Function Directives It is possible to define your own functions in sass and use them in any value or script context. For example:

@media @media directives in Sass behave just like they do in plain CSS, with one extra capability: they can be nested