// No arguments with parenthesis
@mixin foo() {
  color: red;
}

.foo {
  @include foo();
}



// No arguments with no parenthesis
@mixin bar {
  color: orange;
}

.bar {
  @include bar;
}



// Arguments with parenthesis
@mixin baz($color) {
  color: $color;
}

$foo: blue;

.baz {
  @include baz($foo);
}



// Parenthesis only where required
@mixin qux($color: lime) {
  color: $color;
}

.qux {
  @include qux;
}