zooks

$browser-context: 16; // Default

@function rem($pixels, $context: $browser-context) {
  @return #{$pixels/$context}rem;
}

.mt(@time) {
  transition: all @time ease;
}

.header {
  .mt;
}

ol
  li
    ul
      & > li
        margin: 10px 0

.bulleted-menu
  li
    &-subclass
      li
        margin: 10px 0

<ol class="bulleted-menu">
  <li>
    <ul class="bulleted-menu-subclass">
      <li>
…

@keyframes way
  from
    background-position: -1500px 100% 0 0

  to
    background-position: 0 100%