.hljs {
  font-size : 16px;
  line-height : 2;
  font-family : courier;
  background-color: rgba(0, 0, 0, 0.01);
  background-image : linear-gradient(rgba(0,0,0, 0.04) 50%, transparent 0);
  background-size : auto 4em;
  background-origin : content-box;
  border : solid 1px grey;
}