site/src/styles/code-reading.css

/* Excerpt numbers refer to the original source, not to this Markdown page. */
.code-excerpt { --line-start: 0; margin: 1rem 0 1.5rem; }
.code-excerpt pre code { counter-reset: source-line var(--line-start); }
.code-excerpt pre code .line { counter-increment: source-line; }
.code-excerpt pre code .line::before {
  content: counter(source-line);
  display: inline-block;
  width: 3.5em;
  padding-right: 1.2em;
  color: #87909b;
  text-align: right;
  user-select: none;
}
.code-excerpt pre { padding-left: .6rem; }
.reading-start { border-left: 3px solid var(--accent, #c57343); padding-left: 1rem; }
@media (max-width: 720px) {
  .code-excerpt pre { font-size: .78rem; }
  .code-excerpt pre code .line::before { width: 2.8em; padding-right: .8em; }
}