stylus wins.

sample.styl

@import '_common'


/**
 * Clock animation
 */
@keyframes alarm
  from
    transform rotate(-10deg)
  to
    transform rotate(10deg)

svg.icon-clock
  fill $MAGENTA
  animation-name alarm
  animation-direction alternate
  animation-duration .1s
  animation-iteration-count infinite


/**
 * Tweet button
 */
button.tweet
  background $TWITTER_BLUE
  color $WHITE
  border 0
  border-radius .25em
  // padding .5em .667em .5em .5em
  font-weight bold

  .icon-twitter
    fill white
    margin-right .333em