devdocs/assets/stylesheets/pages/_express.scss

._express {
  padding-left: 1rem;

  h1, h2, h3 { margin-left: -1rem; }
  h2 { @extend %block-heading; }
  h3 { @extend %block-label, %label-blue; }
  p > code { @extend %label; }
  .doc-box { @extend %note; }
  .doc-warn { @extend %note-red; }
}