{% highlight 'css' %}
.relative { position: relative }
.absolute { position: absolute }
.fixed    { position: fixed }

.top-0    { top: 0 }
.right-0  { right: 0 }
.bottom-0 { bottom: 0 }
.left-0   { left: 0 }

.z1 { z-index: 1 }
.z2 { z-index: 2 }
.z3 { z-index: 3 }
.z4 { z-index: 4 }

.absolute-center {
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  margin: auto;
  display: table;
}
{% endhighlight %}