@function tracking($target) {
  // 1 unit = 1/1000 em
  @return ($target / 1000) * 1em;
}

@function strip-units($number) {
  @return $number / ($number * 0 + 1);
}

@function sp($value, $baseline:16) {
  @return (strip-units($value) / $baseline) + rem;
}

@function unit($number, $value: 8px) {
  @return $number * $value;
}