reviewable.css

/* Dark Mode */
.diff.line .line.wrapper, .diff.line .empty.line.wrapper .hljs {
  background-color: #f2f2f2;
}

/* Line Numbers */
div[data-line-number]:not([data-line-number="0"]):before {
  content:attr(data-line-number);
  position:absolute;
  color: #444;
  padding: 1px 3px 3px;
  font-size: x-small;
  display: block;
  width: 20px;
  text-align: right;
}
div[data-line-number]:not([data-line-number="0"]) div.hljs {		
  margin-left: 26px;
}