:root {
    --bg: #fbfbf9;
    --fg: #1d1d1b;
    --muted: #6b6b66;
    --line: #dcdcd6;
    --block: #f0f0eb;
    --ok: #1e7a3c;
    --bad: #b3261e;
  }
  @media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) {
      --bg: #161614;
      --fg: #ecece7;
      --muted: #9a9a93;
      --line: #393934;
      --block: #22221f;
      --ok: #6cc586;
      --bad: #ff8a80;
    }
  }
  :root[data-theme="dark"] {
    --bg: #161614;
    --fg: #ecece7;
    --muted: #9a9a93;
    --line: #393934;
    --block: #22221f;
    --ok: #6cc586;
    --bad: #ff8a80;
  }
  body {
    margin: 0;
    padding: 16px;
    background: var(--bg);
    color: var(--fg);
    font: 15px/1.5 system-ui, -apple-system, "Segoe UI", sans-serif;
  }
  main { max-width: 720px; margin: 0 auto; }
  h1 { font-size: 1.4rem; margin: 0.5rem 0 0.25rem; }
  p.lede { color: var(--muted); margin: 0 0 1.25rem; }
  .result { font-size: 1.1rem; margin: 0.5rem 0; }
  .result strong { font-size: 1.6rem; letter-spacing: 0.04em; }
  .pass { color: var(--ok); }
  .fail { color: var(--bad); }
  .muted { color: var(--muted); }
  pre {
    background: var(--block);
    border: 1px solid var(--line);
    border-radius: 6px;
    padding: 12px;
    overflow-x: auto;
    font: 12px/1.45 ui-monospace, Menlo, monospace;
    white-space: pre;
  }
  button {
    margin-top: 8px;
    font: inherit;
    padding: 6px 12px;
    border: 1px solid var(--line);
    border-radius: 6px;
    background: var(--bg);
    color: var(--fg);
    cursor: pointer;
  }
  h2 { font-size: 1rem; margin: 1.5rem 0 0.5rem; }