Added something about argument-less mixins

_includes/snippets/mixins/08/index.html

@@ -0,0 +1,27 @@
+
+<div class="code-block">
+  <div class="code-block__wrapper" data-syntax="scss">
+{% highlight scss %}
+// Yep
+.foo {
+  @include center;
+}
+
+// Nope
+.foo {
+  @include center();
+}
+{% endhighlight %}
+  </div>
+  <div class="code-block__wrapper" data-syntax="sass">
+{% highlight sass %}
+// Yep
+.foo
+  +center
+
+// Nope
+.foo
+  +center()
+{% endhighlight %}
+  </div>
+</div>

en/_mixins.md

@@ -23,6 +23,14 @@ Another valid example would be a mixin to size an element, defining both `width`
 * [A Sass Mixin for CSS Triangles](http://www.sitepoint.com/sass-mixin-css-triangles/)
 * [Building a Linear-Gradient Mixin](http://www.sitepoint.com/building-linear-gradient-mixin-sass/)
 
+## Argument-less mixins
+
+Sometimes mixins are used only to avoid repeating the same group of declarations over and over again, yet do not need any parameter or have sensible enough defaults so that we don’t necessarily have to pass arguments.
+
+In such cases, we can safely omit the parentheses when calling them. The `@include` keyword (or `+` sign in indented-syntax) already acts as a indicator that the line is a mixin call; there is no need for extra parentheses here.
+
+{% include snippets/mixins/08/index.html %}
+
 ## Arguments list
 
 When dealing with an unknown number of arguments in a mixin, always use an `arglist` rather than a list. Think of `arglist` as the 8th hidden undocumented data type from Sass that is implicitly used when passing an arbitrary number of arguments to a mixin or a function whose signature contains `...`.