.up::before,
.down::before {
  content: "";
  display: inline-block;
  width: 12px;
  height: 12px;
  margin-right: 6px;
  background-repeat: no-repeat;
  background-position: center;
  background-size: contain;
}

.up::before {
  background-image: asset-url('arrow_up.svg');
}

.down::before {
  background-image: asset-url('arrow_down.svg');
}