:root {
  --bg: #f7f7f5;
  --surface: #ffffff;
  --surface-2: #f0efec;
  --text: #1d1d1f;
  --muted: #5f6368;
  --border: #e2e0db;
  --accent: #c8102e;
  --accent-soft: #fbe9ec;
  --link: #b00d27;
  --bs: #1f4e9c;
  --bs-soft: #e8eefa;
  --nfpa: #b4231f;
  --nfpa-soft: #fbeceb;
  --diff: #a15c00;
  --diff-soft: #fff4df;
  --dow: #6a2c91;
  --dow-soft: #f3eaf9;
  --ok: #1e7a3c;
  --ok-soft: #e6f4ea;
  --bad: #b3261e;
  --bad-soft: #fce8e6;
  --info: #455a64;
  --info-soft: #eceff1;
  --radius: 10px;
  --shadow: 0 1px 2px rgba(0,0,0,.05), 0 2px 8px rgba(0,0,0,.05);
  --sidebar: 270px;
  --topbar: 56px;
  --font: system-ui, -apple-system, "Segoe UI", Roboto, Arial, sans-serif;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #141416; --surface: #1c1c1f; --surface-2: #26262a; --text: #ececee; --muted: #a0a0a8; --border: #333338;
    --accent: #ff5a6e; --accent-soft: #3a1d22; --link: #ff8a98;
    --bs: #8db4ff; --bs-soft: #1b2638; --nfpa: #ff8a80; --nfpa-soft: #3a1f1d; --diff: #ffc266; --diff-soft: #3a2c14;
    --dow: #d4a6f5; --dow-soft: #2d1f38; --ok: #7ad69a; --ok-soft: #173322; --bad: #ff8a80; --bad-soft: #3a1d1b;
    --info: #b0bec5; --info-soft: #24292c;
  }
}
:root[data-theme="dark"] {
  --bg: #141416; --surface: #1c1c1f; --surface-2: #26262a; --text: #ececee; --muted: #a0a0a8; --border: #333338;
  --accent: #ff5a6e; --accent-soft: #3a1d22; --link: #ff8a98;
  --bs: #8db4ff; --bs-soft: #1b2638; --nfpa: #ff8a80; --nfpa-soft: #3a1f1d; --diff: #ffc266; --diff-soft: #3a2c14;
  --dow: #d4a6f5; --dow-soft: #2d1f38; --ok: #7ad69a; --ok-soft: #173322; --bad: #ff8a80; --bad-soft: #3a1d1b;
  --info: #b0bec5; --info-soft: #24292c;
}

* { box-sizing: border-box; }
html { scroll-padding-top: calc(var(--topbar) + 12px); }
body { margin: 0; background: var(--bg); color: var(--text); font: 16px/1.6 var(--font); -webkit-text-size-adjust: 100%; }
a { color: var(--link); }
img { max-width: 100%; height: auto; border-radius: var(--radius); }

/* ---------- top bar ---------- */
.topbar { position: sticky; top: 0; z-index: 30; height: var(--topbar); display: flex; align-items: center; gap: 12px; padding: 0 16px; background: var(--surface); border-bottom: 1px solid var(--border); }
.brand { display: flex; align-items: center; gap: 8px; text-decoration: none; color: var(--text); font-weight: 700; white-space: nowrap; }
.brand-mark { font-size: 22px; }
.search { position: relative; flex: 1; max-width: 520px; margin-left: auto; }
.search input { width: 100%; height: 38px; padding: 0 12px; border: 1px solid var(--border); border-radius: 8px; background: var(--surface-2); color: var(--text); font: inherit; }
.search input:focus { outline: 2px solid var(--accent); outline-offset: 0; }
.search-results { position: absolute; top: 44px; left: 0; right: 0; max-height: 70vh; overflow: auto; background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); box-shadow: 0 8px 30px rgba(0,0,0,.15); }
.search-results a { display: block; padding: 10px 14px; text-decoration: none; color: var(--text); border-bottom: 1px solid var(--border); }
.search-results a:hover, .search-results a.sel { background: var(--surface-2); }
.search-results small { display: block; color: var(--muted); }
.search-results .snip { font-size: 14px; color: var(--muted); }
.search-results mark { background: var(--diff-soft); color: inherit; }
.who { font-size: 13px; color: var(--muted); white-space: nowrap; }
.icon-btn { border: 1px solid var(--border); background: var(--surface); color: var(--text); width: 38px; height: 38px; border-radius: 8px; font-size: 18px; cursor: pointer; }
.menu-btn { display: none; }

/* ---------- shell ---------- */
.shell { display: grid; grid-template-columns: var(--sidebar) minmax(0, 1fr) 220px; max-width: 1440px; margin: 0 auto; }
body.wide .shell, body.home .shell { grid-template-columns: var(--sidebar) minmax(0, 1fr) 0; }
.scrim { display: none; }
.sidebar { position: sticky; top: var(--topbar); height: calc(100vh - var(--topbar)); overflow-y: auto; padding: 16px 12px 40px; border-right: 1px solid var(--border); }
.rightbar { position: sticky; top: var(--topbar); height: calc(100vh - var(--topbar)); overflow-y: auto; padding: 24px 12px; }
.main { min-width: 0; padding: 24px 40px 80px; }
.content { max-width: 820px; }
body.wide .content, body.home .content { max-width: 1040px; }

/* nav */
.nav-link { display: block; padding: 6px 10px; border-radius: 6px; color: var(--text); text-decoration: none; font-size: 15px; }
.nav-link:hover { background: var(--surface-2); }
.nav-link.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.nav-link.is-read::after { content: " ✔"; color: var(--ok); font-size: 12px; }
.nav-heading { margin: 18px 10px 6px; font-size: 12px; text-transform: uppercase; letter-spacing: .06em; color: var(--muted); font-weight: 700; }
.nav-module { margin: 2px 0; }
.nav-module summary { cursor: pointer; padding: 7px 10px; border-radius: 6px; font-weight: 600; list-style: none; display: flex; align-items: center; gap: 6px; }
.nav-module summary::-webkit-details-marker { display: none; }
.nav-module summary::after { content: "›"; margin-left: auto; transition: transform .15s; color: var(--muted); }
.nav-module[open] summary::after { transform: rotate(90deg); }
.nav-module summary:hover { background: var(--surface-2); }
.nav-module .nav-link { margin-left: 22px; font-size: 14px; }
.nav-module.planned { padding: 7px 10px; color: var(--muted); display: flex; gap: 6px; align-items: center; font-size: 15px; }
.nav-icon { width: 20px; text-align: center; }
.soon { margin-left: auto; font-size: 11px; padding: 1px 7px; border-radius: 99px; background: var(--surface-2); color: var(--muted); }

/* toc */
.toc-title { font-size: 12px; text-transform: uppercase; letter-spacing: .06em; color: var(--muted); font-weight: 700; margin-bottom: 8px; }
.toc a { display: block; font-size: 13px; color: var(--muted); text-decoration: none; padding: 3px 0; line-height: 1.35; }
.toc a:hover { color: var(--accent); }
.toc .toc-3 { padding-left: 12px; }

/* ---------- typography ---------- */
.crumbs { font-size: 13px; color: var(--muted); margin-bottom: 12px; }
.crumbs a { color: var(--muted); }
.crumbs .sep { margin: 0 6px; }
h1 { font-size: 2rem; line-height: 1.2; margin: 0 0 12px; }
h2 { font-size: 1.45rem; margin: 2.2em 0 .6em; padding-bottom: 6px; border-bottom: 1px solid var(--border); }
h3 { font-size: 1.15rem; margin: 1.8em 0 .5em; }
h1, h2, h3, h4 { position: relative; }
.anchor { position: absolute; left: -1em; color: var(--muted); text-decoration: none; opacity: 0; font-weight: 400; }
h2:hover .anchor, h3:hover .anchor { opacity: 1; }
.lede { font-size: 1.1rem; color: var(--muted); }
code { background: var(--surface-2); padding: 1px 5px; border-radius: 4px; font-size: .9em; }
pre { background: var(--surface-2); padding: 12px; border-radius: var(--radius); overflow: auto; }
blockquote { margin: 1em 0; padding: 4px 16px; border-left: 4px solid var(--border); color: var(--muted); }
hr { border: 0; border-top: 1px solid var(--border); margin: 2em 0; }
li { margin: .25em 0; }

/* tables */
.table-wrap { overflow-x: auto; margin: 1em 0; border: 1px solid var(--border); border-radius: var(--radius); background: var(--surface); }
table { border-collapse: collapse; width: 100%; font-size: 15px; }
th, td { padding: 9px 12px; border-bottom: 1px solid var(--border); text-align: left; vertical-align: top; }
th { background: var(--surface-2); font-weight: 700; white-space: nowrap; }
tr:last-child td { border-bottom: 0; }

/* badges */
.badge { display: inline-block; font-size: 11px; font-weight: 800; letter-spacing: .04em; padding: 1px 7px; border-radius: 99px; vertical-align: 2px; line-height: 1.6; }
.badge-bs { background: var(--bs-soft); color: var(--bs); }
.badge-nfpa { background: var(--nfpa-soft); color: var(--nfpa); }
.badge-dow { background: var(--dow-soft); color: var(--dow); }
.badge-diff { background: var(--diff-soft); color: var(--diff); }
.badge-verify { background: var(--info-soft); color: var(--info); border: 1px dashed var(--info); }

/* callouts */
.callout { margin: 1.4em 0; border-radius: var(--radius); border-left: 5px solid; padding: 12px 16px; background: var(--surface); box-shadow: var(--shadow); }
.callout-title { font-weight: 700; display: flex; gap: 8px; align-items: center; }
.callout-body > :first-child { margin-top: 6px; }
.callout-body > :last-child { margin-bottom: 0; }
.callout-bs { border-color: var(--bs); background: var(--bs-soft); } .callout-bs .callout-title { color: var(--bs); }
.callout-nfpa { border-color: var(--nfpa); background: var(--nfpa-soft); } .callout-nfpa .callout-title { color: var(--nfpa); }
.callout-diff { border-color: var(--diff); background: var(--diff-soft); } .callout-diff .callout-title { color: var(--diff); }
.callout-dow { border-color: var(--dow); background: var(--dow-soft); } .callout-dow .callout-title { color: var(--dow); }
.callout-safety { border-color: var(--bad); background: var(--bad-soft); } .callout-safety .callout-title { color: var(--bad); }
.callout-tip { border-color: var(--ok); background: var(--ok-soft); } .callout-tip .callout-title { color: var(--ok); }
.callout-info, .callout-why { border-color: var(--info); background: var(--info-soft); }
.callout-verify { border-color: var(--info); border-left-style: dashed; background: var(--info-soft); }

/* flowcharts */
.flow { margin: 1.5em 0; background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 12px; }
.flow-scroll { overflow-x: auto; }
.flow pre.mermaid { background: transparent; margin: 0; text-align: center; min-height: 60px; }
.flow figcaption { font-size: 12px; color: var(--muted); text-align: center; margin-top: 6px; display: none; }
@media (max-width: 700px) { .flow figcaption { display: block; } }

/* layer tag & std pair */
.layer-tag { display: inline-block; font-size: 12px; font-weight: 700; text-transform: uppercase; letter-spacing: .06em; color: var(--accent); margin-bottom: 4px; }
.std-pair { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin: 16px 0; }
.std-pair > div { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 12px; font-size: 14px; }

/* steps */
.steps { list-style: none; padding: 0; counter-reset: s; display: grid; gap: 8px; }
.steps li { counter-increment: s; margin: 0; }
.steps a { display: flex; align-items: center; gap: 12px; padding: 12px 14px; background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); text-decoration: none; color: var(--text); font-weight: 600; }
.steps a::before { content: counter(s); flex: none; width: 28px; height: 28px; border-radius: 50%; display: grid; place-items: center; background: var(--surface-2); color: var(--muted); font-size: 14px; }
.steps a.is-read::before { content: "✔"; background: var(--ok-soft); color: var(--ok); }
.steps a:hover { border-color: var(--accent); }
.steps .layer { font-size: 11px; text-transform: uppercase; letter-spacing: .05em; color: var(--accent); font-weight: 700; min-width: 0; }
.steps a .layer + * { font-weight: 600; }

/* home */
.hero { background: linear-gradient(135deg, var(--accent-soft), var(--surface)); border: 1px solid var(--border); border-radius: 16px; padding: 28px; margin-bottom: 8px; }
.hero h1 { font-size: 2.2rem; }
.cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 14px; }
.card { position: relative; display: block; padding: 18px; background: var(--surface); border: 1px solid var(--border); border-radius: 14px; text-decoration: none; color: var(--text); box-shadow: var(--shadow); transition: transform .12s, border-color .12s; }
a.card:hover { transform: translateY(-2px); border-color: var(--accent); }
.card h3 { margin: 6px 0 4px; }
.card p { margin: 0 0 10px; font-size: 14px; color: var(--muted); }
.card-icon { font-size: 30px; }
.card-num { position: absolute; top: 12px; right: 14px; font-size: 13px; color: var(--muted); font-weight: 700; }
.card.planned { opacity: .6; box-shadow: none; background: transparent; border-style: dashed; }

/* progress bars */
.bar { height: 8px; background: var(--surface-2); border-radius: 99px; overflow: hidden; }
.bar > span { display: block; height: 100%; background: var(--ok); border-radius: 99px; transition: width .3s; }
.module-progress { margin: 12px 0; }
.module-progress .meta { display: flex; flex-wrap: wrap; gap: 6px 16px; font-size: 13px; color: var(--muted); margin-top: 6px; }
.module-progress.compact .meta { font-size: 12px; }

/* buttons */
.btn { display: inline-flex; align-items: center; gap: 6px; padding: 10px 18px; min-height: 44px; border-radius: 8px; border: 1px solid var(--border); background: var(--surface); color: var(--text); font: inherit; font-weight: 600; cursor: pointer; text-decoration: none; }
.btn:hover { border-color: var(--accent); }
.btn-primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn-primary:hover { filter: brightness(1.08); }
.btn[disabled] { opacity: .5; cursor: default; }
.btn-read.done { background: var(--ok-soft); border-color: var(--ok); color: var(--ok); }
.read-box { margin: 2.5em 0 1em; text-align: center; }

/* prev/next */
.prevnext { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 2em; }
.prevnext a { display: block; padding: 12px 16px; border: 1px solid var(--border); border-radius: var(--radius); text-decoration: none; color: var(--text); font-weight: 600; background: var(--surface); }
.prevnext a:hover { border-color: var(--accent); }
.prevnext small { display: block; font-weight: 400; color: var(--muted); }
.prevnext .next { text-align: right; }

/* review footer */
.review { max-width: 820px; margin-top: 2em; padding: 12px 16px; border-radius: var(--radius); font-size: 14px; }
.review.draft { background: var(--diff-soft); color: var(--text); border: 1px dashed var(--diff); }
.review.ok { background: var(--ok-soft); }
.review .sources { color: var(--muted); font-size: 13px; margin-top: 4px; }

/* ---------- quiz ---------- */
.panel { background: var(--surface); border: 1px solid var(--border); border-radius: 14px; padding: 20px; box-shadow: var(--shadow); }
.quiz-modes { display: grid; gap: 10px; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); margin: 12px 0 18px; }
.mode { text-align: left; padding: 14px; border: 2px solid var(--border); border-radius: var(--radius); background: var(--surface); color: var(--text); cursor: pointer; font: inherit; }
.mode strong { display: block; }
.mode small { color: var(--muted); }
.mode.sel { border-color: var(--accent); background: var(--accent-soft); }
.q-head { display: flex; justify-content: space-between; align-items: center; gap: 8px; font-size: 14px; color: var(--muted); margin-bottom: 8px; }
.q-text { font-size: 1.2rem; font-weight: 600; margin: 8px 0 16px; }
.opts { display: grid; gap: 8px; }
.opt { text-align: left; padding: 12px 14px; min-height: 48px; border: 2px solid var(--border); border-radius: var(--radius); background: var(--surface); color: var(--text); font: inherit; cursor: pointer; }
.opt:hover:not([disabled]) { border-color: var(--accent); }
.opt.picked { border-color: var(--bs); background: var(--bs-soft); }
.opt.right { border-color: var(--ok); background: var(--ok-soft); }
.opt.wrong { border-color: var(--bad); background: var(--bad-soft); }
.opt[disabled] { cursor: default; }
.explain { margin-top: 14px; padding: 12px 14px; border-radius: var(--radius); background: var(--surface-2); }
.explain .ref { display: block; margin-top: 6px; font-size: 13px; color: var(--muted); }
.q-actions { display: flex; justify-content: flex-end; gap: 10px; margin-top: 16px; }
.score-big { font-size: 3rem; font-weight: 800; margin: 0; }
.pass { color: var(--ok); } .fail { color: var(--bad); }
.review-list { margin-top: 16px; }
.review-item { border-top: 1px solid var(--border); padding: 12px 0; }
.qbar { height: 6px; background: var(--surface-2); border-radius: 99px; overflow: hidden; margin-bottom: 14px; }
.qbar span { display: block; height: 100%; background: var(--accent); }

/* flashcards */
.fc-wrap { perspective: 1200px; margin: 16px 0; }
.fc { position: relative; min-height: 240px; cursor: pointer; transform-style: preserve-3d; transition: transform .45s; }
.fc.flipped { transform: rotateY(180deg); }
.fc-face { position: absolute; inset: 0; display: flex; flex-direction: column; justify-content: center; align-items: center; text-align: center; padding: 24px; border-radius: 16px; border: 1px solid var(--border); background: var(--surface); box-shadow: var(--shadow); backface-visibility: hidden; -webkit-backface-visibility: hidden; font-size: 1.15rem; }
.fc-back { transform: rotateY(180deg); background: var(--surface-2); }
.fc-face small { position: absolute; top: 12px; left: 16px; font-size: 12px; color: var(--muted); text-transform: uppercase; letter-spacing: .05em; }
.fc-btns { display: flex; gap: 10px; justify-content: center; flex-wrap: wrap; }

/* signoff */
.so-item { display: flex; gap: 12px; align-items: flex-start; padding: 14px 0; border-bottom: 1px solid var(--border); }
.so-item:last-child { border-bottom: 0; }
.so-tick { flex: none; width: 30px; height: 30px; border-radius: 8px; border: 2px solid var(--border); display: grid; place-items: center; font-weight: 800; background: var(--surface); color: var(--ok); }
.so-item.signed .so-tick { border-color: var(--ok); background: var(--ok-soft); }
.so-text { flex: 1; }
.so-meta { font-size: 13px; color: var(--muted); }
.so-actions { display: flex; gap: 6px; flex-wrap: wrap; margin-top: 6px; }
.so-actions input { flex: 1; min-width: 160px; height: 36px; padding: 0 10px; border: 1px solid var(--border); border-radius: 8px; background: var(--surface); color: var(--text); font: inherit; font-size: 14px; }
.so-actions .btn { min-height: 36px; padding: 4px 12px; font-size: 14px; }
.toolbar { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; margin: 12px 0; }
.toolbar select { height: 38px; border-radius: 8px; border: 1px solid var(--border); padding: 0 10px; background: var(--surface); color: var(--text); font: inherit; }
.notice { padding: 10px 14px; border-radius: var(--radius); background: var(--info-soft); font-size: 14px; margin: 12px 0; }

/* progress page */
.prog-table td:nth-child(n+2) { white-space: nowrap; }
.pill { display: inline-block; padding: 1px 8px; border-radius: 99px; font-size: 12px; font-weight: 700; }
.pill.ok { background: var(--ok-soft); color: var(--ok); }
.pill.no { background: var(--surface-2); color: var(--muted); }
.pill.bad { background: var(--bad-soft); color: var(--bad); }

/* ---------- responsive ---------- */
@media (max-width: 1180px) {
  .shell, body.wide .shell, body.home .shell { grid-template-columns: var(--sidebar) minmax(0, 1fr); }
  .rightbar { display: none; }
}
@media (max-width: 860px) {
  .menu-btn { display: block; }
  .shell, body.wide .shell, body.home .shell { grid-template-columns: minmax(0, 1fr); }
  .sidebar { position: fixed; z-index: 40; top: var(--topbar); left: 0; width: min(85vw, 320px); background: var(--surface); transform: translateX(-100%); transition: transform .2s; box-shadow: 0 0 30px rgba(0,0,0,.2); }
  body.nav-open .sidebar { transform: none; }
  .scrim { display: none; }
  body.nav-open .scrim { display: block; position: fixed; inset: var(--topbar) 0 0 0; background: rgba(0,0,0,.35); z-index: 35; }
  .main { padding: 16px 16px 60px; }
  .brand-name { display: none; }
  .who { display: none; }
  h1 { font-size: 1.6rem; }
  .hero { padding: 18px; }
  .hero h1 { font-size: 1.7rem; }
  .std-pair, .prevnext { grid-template-columns: 1fr; }
  .anchor { display: none; }
  th, td { min-width: 140px; }
  th:first-child, td:first-child { min-width: 110px; }
}
@media print {
  .topbar, .sidebar, .rightbar, .prevnext, .read-box { display: none !important; }
  .shell { display: block; }
  .callout { box-shadow: none; }
}