:root {
  --bg: #f6f7f9;
  --surface: #ffffff;
  --text: #1c2330;
  --muted: #5d6879;
  --border: #e2e6ec;
  --accent: #2f5bd3;
  --accent-soft: #e8eefc;
  --ok: #1d8a4e;
  --ok-soft: #e4f5eb;
  --bad: #c43d3d;
  --bad-soft: #fbe9e9;
  --warn-soft: #fff5de;
  --warn: #a86b00;
  --exam-soft: #efe9fc;
  --exam: #6a3fc4;
  --sidebar-w: 270px;
  --topbar-h: 52px;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #12151b;
    --surface: #1b2029;
    --text: #e4e8ee;
    --muted: #97a1b0;
    --border: #2c333f;
    --accent: #7ea2ff;
    --accent-soft: #232e48;
    --ok: #5fcf8e;
    --ok-soft: #173325;
    --bad: #f08080;
    --bad-soft: #3a1f22;
    --warn-soft: #3a2f16;
    --warn: #f0b85a;
    --exam-soft: #2b2342;
    --exam: #b9a0f5;
  }
}

* { box-sizing: border-box; }
html, body { margin: 0; }
body {
  background: var(--bg);
  color: var(--text);
  font: 16px/1.6 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  -webkit-text-size-adjust: 100%;
}
a { color: var(--accent); text-decoration: none; }
h1 { font-size: 1.6rem; line-height: 1.25; margin: 0.2rem 0 0.4rem; }
h2 { font-size: 1.15rem; margin: 0.3rem 0; }
h3 { font-size: 1rem; margin: 0; }
.muted { color: var(--muted); }
.small { font-size: 0.85rem; }
.pad { padding: 0 16px; }
b, strong { font-weight: 650; }

/* ---------- cards / buttons ---------- */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 16px;
  margin-bottom: 14px;
}
.btn {
  display: inline-block;
  font: inherit; font-size: 0.9rem;
  padding: 7px 14px;
  border-radius: 8px;
  border: 1px solid var(--accent);
  background: var(--accent);
  color: #fff;
  cursor: pointer;
}
.btn.ghost { background: transparent; color: var(--accent); }
.btn:hover { filter: brightness(1.08); }
.icon-btn { font-size: 1.3rem; background: none; border: 0; color: var(--text); cursor: pointer; padding: 4px 8px; }
.check { display: inline-flex; gap: 6px; align-items: center; cursor: pointer; font-size: 0.9rem; color: var(--muted); }
.check.big { font-size: 1rem; color: var(--text); }
.check input { width: 18px; height: 18px; accent-color: var(--ok); }

/* ---------- landing ---------- */
.landing { max-width: 960px; margin: 0 auto; padding: 32px 16px; }
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 14px; margin-top: 20px; }
.subject { color: var(--text); transition: transform .12s, border-color .12s; display: block; }
.subject:hover { transform: translateY(-2px); border-color: var(--accent); }
.subject .code { font-size: 0.75rem; font-weight: 700; letter-spacing: .06em; color: var(--accent); }
.progress { height: 6px; background: var(--border); border-radius: 3px; overflow: hidden; margin: 10px 0 6px; }
.progress div { height: 100%; background: var(--ok); }

/* ---------- layout ---------- */
.topbar {
  position: sticky; top: 0; z-index: 30;
  height: var(--topbar-h);
  display: flex; align-items: center; gap: 12px;
  padding: 0 12px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}
.brand { font-size: 0.9rem; white-space: nowrap; }
.topbar-title { font-weight: 600; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.menu-btn { display: none; }

.sidebar {
  position: fixed; top: var(--topbar-h); bottom: 0; left: 0;
  width: var(--sidebar-w);
  overflow-y: auto;
  background: var(--surface);
  border-right: 1px solid var(--border);
  padding: 12px 8px;
  z-index: 20;
}
.side-title { font-size: 0.75rem; font-weight: 700; letter-spacing: .06em; text-transform: uppercase; color: var(--muted); padding: 4px 10px 10px; }
.side-item {
  display: flex; gap: 10px; align-items: center;
  padding: 9px 10px; border-radius: 8px;
  color: var(--text); font-size: 0.92rem;
}
.side-item:hover { background: var(--bg); }
.side-item.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.side-item.pending { color: var(--muted); }
.sn {
  flex: none; width: 26px; height: 26px; border-radius: 50%;
  display: grid; place-items: center;
  font-size: 0.8rem; font-weight: 700;
  border: 1px solid var(--border); background: var(--bg);
}
.side-item.active .sn { border-color: var(--accent); }
.main { margin-left: var(--sidebar-w); }
.session { max-width: 860px; margin: 0 auto; padding: 24px 20px 60px; }
.eyebrow { font-size: 0.8rem; font-weight: 700; letter-spacing: .05em; color: var(--accent); text-transform: uppercase; }
.session-head { margin-bottom: 16px; }
.scrim { display: none; }

@media (max-width: 820px) {
  .menu-btn { display: block; }
  .brand { display: none; }
  .sidebar { transform: translateX(-100%); transition: transform .2s ease; box-shadow: 4px 0 20px rgba(0,0,0,.15); }
  .sidebar.open { transform: none; }
  .scrim.show { display: block; position: fixed; inset: var(--topbar-h) 0 0 0; background: rgba(0,0,0,.35); z-index: 15; }
  .main { margin-left: 0; }
  .session { padding: 18px 16px 60px; }
  h1 { font-size: 1.35rem; }
}
@media (max-width: 820px) {
  .topbar .brand-mobile { display: inline; }
}

/* ---------- tabs ---------- */
.tabs {
  position: sticky; top: var(--topbar-h); z-index: 10;
  display: flex; gap: 4px;
  background: var(--bg);
  padding: 8px 0;
  margin-bottom: 8px;
  overflow-x: auto;
}
.tabs button {
  flex: 1 0 auto;
  font: inherit; font-size: 0.92rem;
  padding: 9px 14px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
  border-radius: 10px;
  cursor: pointer;
}
.tabs button.on { background: var(--accent); border-color: var(--accent); color: #fff; font-weight: 600; }

/* ---------- notes ---------- */
.overview { background: var(--accent-soft); border-radius: 12px; padding: 14px 16px; margin-bottom: 12px; }
.overview .md { display: inline; }
.chips { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 14px; }
.chips a {
  font-size: 0.82rem; padding: 4px 10px; border-radius: 999px;
  border: 1px solid var(--border); background: var(--surface); color: var(--text);
}
.chips a:hover { border-color: var(--accent); color: var(--accent); }
.section { padding: 0; overflow: hidden; scroll-margin-top: calc(var(--topbar-h) + 60px); }
.section-head {
  width: 100%;
  display: flex; justify-content: space-between; align-items: center; gap: 10px;
  padding: 14px 16px;
  background: none; border: 0; color: var(--text);
  font: inherit; font-weight: 650; font-size: 1.05rem; text-align: left;
  cursor: pointer;
}
.section-head.static { cursor: default; }
.section-head .meta { display: flex; align-items: center; gap: 8px; flex: none; }
.slides { font-size: 0.72rem; font-weight: 500; color: var(--muted); border: 1px solid var(--border); border-radius: 999px; padding: 1px 8px; }
.chev { transition: transform .15s; transform: rotate(-90deg); color: var(--muted); }
.chev.open { transform: none; }
.section-body { padding: 0 16px 16px; border-top: 1px solid var(--border); padding-top: 12px; }

.md p { margin: 0.5rem 0; }
.md > :first-child { margin-top: 0; }
.md > :last-child { margin-bottom: 0; }
.md ul, .md ol, .list { padding-left: 1.3rem; margin: 0.4rem 0 0.8rem; }
.list li, .md li { margin: 0.25rem 0; }
.md code { background: var(--bg); padding: 1px 5px; border-radius: 4px; font-size: .9em; }
.md table, .table-wrap table { border-collapse: collapse; width: 100%; font-size: 0.9rem; }
.md table { display: block; overflow-x: auto; margin: 0.6rem 0; }
.table-wrap { overflow-x: auto; margin: 0.6rem 0 1rem; }
th, td { border: 1px solid var(--border); padding: 7px 9px; text-align: left; vertical-align: top; }
th { background: var(--bg); font-weight: 650; }
.caption { font-size: 0.82rem; color: var(--muted); margin-bottom: 4px; }
.katex-display { overflow-x: auto; overflow-y: hidden; padding: 4px 0; }

.callout { border-radius: 10px; padding: 12px 14px; margin: 0.8rem 0; border-left: 4px solid; }
.callout.tip { background: var(--accent-soft); border-color: var(--accent); }
.callout.warn { background: var(--warn-soft); border-color: var(--warn); }
.callout.exam { background: var(--exam-soft); border-color: var(--exam); }
.callout-title { font-weight: 700; margin-bottom: 4px; }

.terms { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 10px; }
.term { background: var(--bg); border-radius: 8px; padding: 10px 12px; font-size: 0.9rem; display: flex; flex-direction: column; gap: 2px; }

.diagram { margin: 0.8rem 0; text-align: center; }
.diagram svg { width: 100%; max-width: 560px; height: auto; }
.diagram figcaption { font-size: 0.85rem; color: var(--muted); }
.dg-title { font-size: 13px; font-weight: 700; fill: var(--text); text-anchor: middle; }
.dg-t { font-size: 12px; fill: var(--text); text-anchor: middle; }
.dg-t.sm { font-size: 9px; }
.dg-in { fill: var(--bg); stroke: var(--border); }
.dg-box { fill: var(--accent-soft); stroke: var(--accent); }
.dg-out { fill: var(--bg); stroke: var(--border); }
.dg-out.hl { fill: var(--ok-soft); stroke: var(--ok); }
.dg-line { stroke: var(--muted); stroke-width: 1.5; fill: none; }
.dg-arrow { fill: var(--muted); }

/* ---------- problems ---------- */
.toolbar { display: flex; flex-wrap: wrap; align-items: center; gap: 10px; justify-content: space-between; margin-bottom: 12px; }
.seg { display: flex; border: 1px solid var(--border); border-radius: 8px; overflow: hidden; }
.seg button { font: inherit; font-size: 0.85rem; padding: 6px 12px; border: 0; background: var(--surface); color: var(--text); cursor: pointer; }
.seg button + button { border-left: 1px solid var(--border); }
.seg button.on { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.problem header { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; margin-bottom: 10px; }
.problem header h3 { flex: 1 1 200px; }
.problem.is-solved { border-color: var(--ok); }
.qnum {
  display: inline-grid; place-items: center; min-width: 30px; height: 26px; padding: 0 6px;
  border-radius: 6px; background: var(--accent-soft); color: var(--accent); font-weight: 700; font-size: 0.8rem;
}
.badge { font-size: 0.72rem; font-weight: 600; padding: 2px 8px; border-radius: 999px; border: 1px solid var(--border); }
.badge.easy { background: var(--ok-soft); color: var(--ok); border-color: transparent; }
.badge.medium { background: var(--warn-soft); color: var(--warn); border-color: transparent; }
.badge.hard { background: var(--bad-soft); color: var(--bad); border-color: transparent; }
.badge.marks { color: var(--muted); }
.problem-actions { display: flex; flex-wrap: wrap; align-items: center; gap: 14px; margin-top: 12px; }
.solution { margin-top: 14px; padding: 14px; background: var(--bg); border-radius: 10px; border-left: 4px solid var(--ok); }
.sol-label { font-size: 0.75rem; font-weight: 700; text-transform: uppercase; letter-spacing: .06em; color: var(--ok); margin-bottom: 6px; }

/* ---------- quiz ---------- */
.quiz-q { display: flex; gap: 10px; align-items: flex-start; font-weight: 600; margin-bottom: 10px; }
.options { display: grid; gap: 8px; }
.opt {
  display: flex; gap: 10px; align-items: center; text-align: left;
  font: inherit; font-size: 0.93rem;
  padding: 10px 12px; border-radius: 10px;
  border: 1px solid var(--border); background: var(--surface); color: var(--text);
  cursor: pointer;
}
.opt:hover:not(:disabled) { border-color: var(--accent); }
.opt:disabled { cursor: default; }
.opt-letter { flex: none; width: 24px; height: 24px; border-radius: 50%; display: grid; place-items: center; background: var(--bg); font-size: 0.8rem; font-weight: 700; }
.opt.correct { border-color: var(--ok); background: var(--ok-soft); }
.opt.wrong { border-color: var(--bad); background: var(--bad-soft); }
.why { margin-top: 10px; font-size: 0.9rem; padding: 8px 12px; border-radius: 8px; }
.why .md { display: inline; }
.why.ok { background: var(--ok-soft); }
.why.no { background: var(--bad-soft); }
.final { text-align: center; font-size: 1.05rem; }

/* ---------- misc ---------- */
.complete { margin: 24px 0 8px; padding: 14px 16px; border: 1px dashed var(--border); border-radius: 12px; }
.pager { display: flex; justify-content: space-between; gap: 10px; flex-wrap: wrap; margin-top: 16px; }
.pager .btn { max-width: 100%; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.empty { text-align: center; }
.loading { padding: 40px; text-align: center; color: var(--muted); }
.badge.pyq { background: var(--exam-soft); color: var(--exam); border-color: transparent; }
.side-title.group { margin-top: 14px; border-top: 1px solid var(--border); padding-top: 14px; }

/* ---------- flow diagrams (```flow blocks) ---------- */
.flow { display: flex; flex-direction: column; gap: 8px; margin: 0.8rem 0; padding: 12px; border: 1px dashed var(--border); border-radius: 10px; background: var(--bg); }
.flow-row { display: flex; flex-wrap: wrap; align-items: center; gap: 6px; }
.flow-step { padding: 6px 10px; border-radius: 8px; border: 1px solid var(--accent); background: var(--accent-soft); font-size: 0.85rem; font-weight: 600; }
.flow-arrow { color: var(--muted); font-weight: 700; }
.md pre { background: var(--bg); border: 1px solid var(--border); border-radius: 8px; padding: 10px 12px; overflow-x: auto; font-size: 0.85rem; }
.md pre code { background: none; padding: 0; }
.md ul ul, .md ol ul { margin: 0.2rem 0; }
.flow-row + .flow-row { border-top: 1px dashed var(--border); padding-top: 8px; }
@media (max-width: 640px) {
  .flow-row { flex-direction: column; align-items: stretch; gap: 2px; }
  .flow-arrow { transform: rotate(90deg); align-self: center; line-height: 1; }
  .flow-step { text-align: center; }
}

/* ---------- teaching blocks ---------- */
.callout.idea { background: var(--ok-soft); border-color: var(--ok); }
.callout.example { background: var(--bg); border-color: var(--muted); border: 1px solid var(--border); border-left: 4px solid var(--muted); }
.callout.formula { background: var(--surface); border: 1px solid var(--accent); border-left: 4px solid var(--accent); }
.callout.formula .katex-display { margin: 0.4rem 0; }
.callout.remember { background: var(--exam-soft); border-color: var(--exam); }
.section-body > .md + .md { margin-top: 0.6rem; }
.section-body h4, .md h4 { font-size: 0.98rem; margin: 1.1rem 0 0.3rem; color: var(--accent); }

/* Solutions: each "### Step" heading becomes a labelled step */
.solution .md h3 {
  font-size: 0.8rem; font-weight: 700; text-transform: uppercase; letter-spacing: .05em;
  color: var(--accent); margin: 1.1rem 0 0.35rem; padding-top: 0.7rem; border-top: 1px dashed var(--border);
}
.solution .md h3:first-child { margin-top: 0; padding-top: 0; border-top: 0; }
.solution .md blockquote { margin: 0.6rem 0; padding: 8px 12px; border-left: 3px solid var(--ok); background: var(--ok-soft); border-radius: 6px; }
.solution .md blockquote p { margin: 0.2rem 0; }

/* ---------- teaching figures (generated SVG, see tools/gen_figures.py) ---------- */
:root {
  --f-s1: #2a78d6; --f-s2: #eb6834; --f-s3: #1baf7a;
  --f-soft1: rgba(42, 120, 214, .12); --f-soft2: rgba(235, 104, 52, .14); --f-soft3: rgba(27, 175, 122, .15);
  --f-good: #0ca30c; --f-bad: #d03b3b;
  --f-goodsoft: rgba(12, 163, 12, .12); --f-badsoft: rgba(208, 59, 59, .12);
}
@media (prefers-color-scheme: dark) {
  :root {
    --f-s1: #3987e5; --f-s2: #d95926; --f-s3: #199e70;
    --f-soft1: rgba(57, 135, 229, .22); --f-soft2: rgba(217, 89, 38, .24); --f-soft3: rgba(25, 158, 112, .25);
    --f-goodsoft: rgba(12, 163, 12, .22); --f-badsoft: rgba(208, 59, 59, .24);
  }
}
.figure { margin: 1rem 0 1.2rem; padding: 12px 10px 8px; background: var(--surface); border: 1px solid var(--border); border-radius: 12px; }
.figure svg.fig { display: block; width: 100%; max-width: 640px; height: auto; margin: 0 auto; }
.figure figcaption { font-size: 0.86rem; color: var(--muted); margin: 8px 4px 2px; line-height: 1.5; }
.figure figcaption .md p { margin: 0; }
.fig text { font-family: inherit; fill: var(--text); }
.fig .t { font-size: 13px; }
.fig .tb { font-size: 13px; font-weight: 650; }
.fig .ts { font-size: 11.5px; }
.fig .ts2 { font-size: 11.5px; fill: var(--muted); }
.fig .mono { font-size: 11px; font-family: ui-monospace, SFMono-Regular, Menlo, monospace; }
.fig .ax, .fig .ax2 { stroke: var(--muted); stroke-width: 1; }
.fig .ax2 { stroke-width: 1.5; }
.fig .gr { stroke: var(--border); stroke-width: 1; }
.fig .guide { stroke: var(--muted); stroke-width: 1.2; stroke-dasharray: 5 4; fill: none; }
.fig .guide2 { stroke: var(--text); stroke-width: 1.5; stroke-dasharray: 6 4; }
.fig .thin { stroke: var(--muted); stroke-width: 1.5; }
.fig .res { stroke: var(--muted); stroke-width: 1.2; stroke-dasharray: 2 3; }
.fig .lg { stroke: var(--muted); stroke-width: 1.5; stroke-dasharray: 4 4; fill: none; }
.fig .l1, .fig .l2, .fig .l3 { fill: none; stroke-width: 2.2; stroke-linecap: round; stroke-linejoin: round; }
.fig .l1 { stroke: var(--f-s1); } .fig .l2 { stroke: var(--f-s2); } .fig .l3 { stroke: var(--f-s3); }
.fig .l2f { fill: none; stroke: var(--f-s2); stroke-width: 2.2; }
.fig .cont { fill: none; stroke: var(--f-s1); stroke-width: 1.2; opacity: .55; }
.fig .d1, .fig .d2, .fig .d3, .fig .dk, .fig .dn { stroke: var(--surface); stroke-width: 2; }
.fig .d1 { fill: var(--f-s1); } .fig .d2 { fill: var(--f-s2); } .fig .d3 { fill: var(--f-s3); }
.fig .dk { fill: var(--text); } .fig .dn { fill: var(--border); stroke: var(--muted); stroke-width: 1; }
.fig .n1 { fill: var(--f-soft1); stroke: var(--f-s1); stroke-width: 1.5; }
.fig .n3 { fill: var(--f-soft3); stroke: var(--f-s3); stroke-width: 1.5; }
.fig .panel { fill: var(--bg); stroke: var(--border); stroke-width: 1; }
.fig .box { fill: var(--f-soft1); stroke: var(--f-s1); stroke-width: 1.2; }
.fig .box2 { fill: var(--f-soft2); stroke: var(--f-s2); stroke-width: 1.2; }
.fig .box3 { fill: var(--f-soft3); stroke: var(--f-s3); stroke-width: 1.2; }
.fig .boxn { fill: var(--bg); stroke: var(--muted); stroke-width: 1; }
.fig .cell1 { fill: var(--f-soft1); stroke: var(--surface); stroke-width: 2; }
.fig .cell2 { fill: var(--f-soft2); stroke: var(--surface); stroke-width: 2; }
.fig .cell3 { fill: var(--f-soft3); stroke: var(--surface); stroke-width: 2; }
.fig .cellx { fill: var(--bg); stroke: var(--muted); stroke-width: 1; stroke-dasharray: 3 3; }
.fig .cg { fill: var(--f-goodsoft); stroke: var(--f-good); stroke-width: 1; }
.fig .cb { fill: var(--f-badsoft); stroke: var(--f-bad); stroke-width: 1; }
.fig .ring1 { fill: none; stroke: var(--f-s1); stroke-width: 2; }
.fig .ring2 { fill: none; stroke: var(--f-s2); stroke-width: 2; stroke-dasharray: 6 3; }
.fig .svring { fill: none; stroke: var(--text); stroke-width: 1.5; }
.fig .zone0 { fill: var(--surface); }
.fig .zone1 { fill: var(--f-soft1); }
.fig .zone2 { fill: var(--bg); }
.fig .area1 { fill: var(--f-soft1); stroke: none; }
.fig .area2 { fill: var(--f-soft2); stroke: none; }
.fig .grp { fill: none; stroke: var(--muted); stroke-width: 1.2; stroke-dasharray: 4 3; }
.fig .grp1 { fill: none; stroke: var(--f-s1); stroke-width: 1.2; opacity: .7; }
.fig .grp2 { fill: none; stroke: var(--f-s2); stroke-width: 1.2; opacity: .7; }
.fig .tg1 { fill: var(--f-soft2); stroke: var(--muted); stroke-width: 1; }
.fig .tg2 { fill: var(--bg); stroke: var(--muted); stroke-width: 1; }
.fig .tg3 { fill: var(--surface); stroke: var(--muted); stroke-width: 1; }
.fig .bar1 { fill: var(--f-s1); } .fig .bar2 { fill: var(--f-s2); }
.fig .arr, .fig .arr1, .fig .arr1b, .fig .arr2, .fig .arr3, .fig .arrk { fill: none; stroke: var(--muted); stroke-width: 1.5; }
.fig .arr1 { stroke: var(--f-s1); stroke-width: 2.2; } .fig .arr1b { stroke: var(--f-s1); stroke-width: 2.2; opacity: .6; }
.fig .arr2 { stroke-dasharray: 5 4; } .fig .arr3 { stroke: var(--f-s3); }
.fig .arrk { stroke: var(--text); stroke-width: 2; }
.fig .ah { fill: var(--muted); }
.fig .under { fill: var(--surface); stroke: none; }

/* ---------- recap tab ---------- */
.recap .section-body { border-top: 0; padding-top: 16px; }
.recap .list li { margin: 0.35rem 0; }
.recap h4 { margin-top: 1.2rem; }
.recap h4:first-child { margin-top: 0; }

/* ---- quiz: one-at-a-time, numeric answers, topics ---- */
.opt.picked { border-color: var(--accent); background: var(--accent-soft); }
.num-answer { display: flex; gap: 10px; align-items: center; }
.num-answer input, input.search { font: inherit; padding: 8px 12px; border: 1px solid var(--border); border-radius: 8px; background: var(--surface); color: var(--text); }
.num-answer input { width: 200px; max-width: 100%; }
input.search { width: 100%; margin-bottom: 6px; }
.wrong-list { margin: 6px 0 0; font-size: 0.88rem; }
.why .solution { margin-top: 8px; background: transparent; }
.seg.wrap { flex-wrap: wrap; }
.badge.topic { margin-left: auto; font-weight: 500; color: var(--muted); white-space: nowrap; }
.quiz-progress { margin-bottom: 4px; }
.problem-actions.center { justify-content: center; margin-top: 12px; }
.final .table-wrap { text-align: left; margin-top: 12px; }
.badge.level-1 { background: var(--ok-soft); color: var(--ok); border-color: transparent; }
.badge.level-2 { background: var(--warn-soft); color: var(--warn); border-color: transparent; }
.badge.level-3 { background: var(--bad-soft); color: var(--bad); border-color: transparent; }
.badge.from-slides { background: var(--accent-soft); color: var(--accent); border-color: transparent; }
.side-toc { margin: 2px 0 6px 38px; border-left: 2px solid var(--border); }
.side-toc a { display: block; padding: 3px 10px; font-size: 0.8rem; color: var(--muted); text-decoration: none; line-height: 1.3; }
.side-toc a:hover { color: var(--accent); }
.toc-toggle { background: none; border: 0; color: var(--muted); cursor: pointer; margin-left: auto; padding: 0 4px; font-size: 0.8rem; }