/* ============================================================
   DCN VIET — MOOC: Truyền thông Dữ liệu & Mạng Máy tính
   ============================================================ */
:root {
  --bg: #f4f7fb;
  --bg-soft: #eaf1f8;
  --surface: #ffffff;
  --surface-2: #f0f5fa;
  --border: #dbe4ef;
  --text: #16283c;
  --text-soft: #51637a;
  --text-faint: #7c8da3;
  --brand: #0e7490;
  --brand-2: #155e93;
  --brand-soft: #e3f2f9;
  --brand-softer: #eef7fb;
  --accent: #f59e0b;
  --ok: #16a34a;
  --ok-soft: #e7f7ed;
  --bad: #dc2626;
  --bad-soft: #fdecec;
  --link: #0b6e8f;
  --code-bg: #10233b;
  --code-text: #d7e6f5;
  --shadow: 0 1px 2px rgba(15, 40, 70, .06), 0 8px 24px rgba(15, 40, 70, .07);
  --shadow-sm: 0 1px 2px rgba(15, 40, 70, .08);
  --radius: 14px;
  --topbar-h: 60px;
  --sidebar-w: 330px;
  --font: "Be Vietnam Pro", "Segoe UI", system-ui, -apple-system, sans-serif;
}
[data-theme="dark"] {
  --bg: #0c1522;
  --bg-soft: #101c2c;
  --surface: #122236;
  --surface-2: #17293f;
  --border: #23384f;
  --text: #dfe9f4;
  --text-soft: #a5b8cc;
  --text-faint: #748aa1;
  --brand: #38bdf8;
  --brand-2: #7dd3fc;
  --brand-soft: #10344a;
  --brand-softer: #0f2c3f;
  --accent: #fbbf24;
  --ok: #4ade80;
  --ok-soft: #123324;
  --bad: #f87171;
  --bad-soft: #3d1517;
  --link: #53c2e8;
  --code-bg: #0a1626;
  --code-text: #cfe3f5;
  --shadow: 0 1px 2px rgba(0, 0, 0, .4), 0 10px 28px rgba(0, 0, 0, .35);
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, .35);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--font);
  font-size: 15.5px;
  line-height: 1.75;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}
img, svg { max-width: 100%; }
a { color: var(--link); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ============================ Topbar ============================ */
.topbar {
  position: sticky; top: 0; z-index: 60;
  height: var(--topbar-h);
  display: flex; align-items: center; gap: 16px;
  padding: 0 18px;
  background: color-mix(in srgb, var(--surface) 88%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}
.brand { display: flex; align-items: center; gap: 10px; color: var(--text); font-size: 19px; }
.brand:hover { text-decoration: none; }
.brand-logo {
  display: grid; place-items: center;
  width: 38px; height: 38px; border-radius: 11px;
  background: linear-gradient(135deg, var(--brand), var(--brand-2));
  font-size: 20px; box-shadow: var(--shadow-sm);
}
.brand-text strong { font-weight: 800; letter-spacing: .3px; }
.brand-text { font-weight: 500; color: var(--text-soft); }
.topbar-links { display: flex; gap: 4px; margin-left: 6px; }
.topbar-links a {
  padding: 7px 12px; border-radius: 9px;
  color: var(--text-soft); font-weight: 600; font-size: 14px;
}
.topbar-links a:hover { background: var(--surface-2); color: var(--text); text-decoration: none; }
.topbar-actions { margin-left: auto; display: flex; align-items: center; gap: 10px; }
.icon-btn {
  display: grid; place-items: center;
  width: 38px; height: 38px; border-radius: 10px;
  border: 1px solid var(--border); background: var(--surface);
  color: var(--text-soft); cursor: pointer; transition: .15s;
}
.icon-btn:hover { background: var(--surface-2); color: var(--text); }
.overall-pill {
  display: flex; align-items: center; gap: 8px;
  padding: 6px 12px; border-radius: 999px;
  background: var(--brand-softer); border: 1px solid var(--border);
  font-size: 13px; font-weight: 700; color: var(--brand);
}
.overall-bar { width: 80px; height: 6px; border-radius: 99px; background: var(--border); overflow: hidden; }
.overall-bar > div { height: 100%; width: 0%; border-radius: 99px; background: linear-gradient(90deg, var(--brand), var(--brand-2)); transition: width .4s; }

/* ============================ Layout ============================ */
.layout { display: grid; grid-template-columns: var(--sidebar-w) 1fr; min-height: calc(100vh - var(--topbar-h)); }
.main {
  min-width: 0;
  padding: 34px 40px 90px;
  max-width: 980px;
  margin: 0 auto;
  width: 100%;
}

/* ============================ Sidebar ============================ */
.sidebar { border-right: 1px solid var(--border); background: var(--surface); position: relative; }
.sidebar-inner {
  position: sticky; top: var(--topbar-h);
  height: calc(100vh - var(--topbar-h));
  display: flex; flex-direction: column;
}
.sidebar-search {
  display: flex; align-items: center; gap: 8px;
  margin: 14px 14px 8px; padding: 0 12px;
  border: 1.5px solid var(--border); border-radius: 10px;
  background: var(--surface-2); color: var(--text-faint);
}
.sidebar-search:focus-within { border-color: var(--brand); }
.sidebar-search input {
  flex: 1; border: none; outline: none; background: transparent;
  padding: 9px 0; font: inherit; font-size: 13.5px; color: var(--text);
}
.sidebar-nav { flex: 1; overflow-y: auto; padding: 4px 10px 18px; }
.sidebar-nav::-webkit-scrollbar { width: 8px; }
.sidebar-nav::-webkit-scrollbar-thumb { background: var(--border); border-radius: 8px; }

.chap-block { margin: 4px 0 6px; }
.chap-head {
  display: flex; align-items: center; gap: 8px;
  width: 100%; padding: 9px 10px; border: none; border-radius: 10px;
  background: transparent; cursor: pointer; text-align: left;
  font: inherit; color: var(--text); font-weight: 700; font-size: 13.5px;
}
.chap-head:hover { background: var(--surface-2); }
.chap-head .chev { margin-left: auto; transition: transform .18s; color: var(--text-faint); flex: none; }
.chap-block.open .chap-head .chev { transform: rotate(90deg); }
.chap-num {
  flex: none; display: inline-grid; place-items: center;
  min-width: 24px; height: 24px; padding: 0 4px; border-radius: 7px;
  background: var(--brand-soft); color: var(--brand);
  font-size: 11.5px; font-weight: 800;
}
.chap-head .done-all { color: var(--ok); font-size: 13px; margin-left: 4px; }
.chap-lessons { display: none; padding: 0 0 6px 8px; }
.chap-block.open .chap-lessons { display: block; }
.chap-block.open { background: var(--brand-softer); border-radius: 12px; }
.lesson-link {
  display: flex; align-items: baseline; gap: 8px;
  padding: 6px 10px 6px 12px; border-radius: 8px;
  color: var(--text-soft); font-size: 13.5px; line-height: 1.45;
  border-left: 2.5px solid transparent;
}
.lesson-link:hover { background: var(--surface-2); color: var(--text); text-decoration: none; }
.lesson-link.active {
  background: var(--brand-soft); color: var(--brand);
  font-weight: 700; border-left-color: var(--brand);
}
.lesson-link .tick {
  flex: none; font-size: 12px; color: var(--ok); align-self: center;
  width: 16px; text-align: center;
}
.lesson-link .tick.empty { color: var(--border); }
.chap-meta { font-size: 11px; color: var(--text-faint); font-weight: 600; margin-left: auto; white-space: nowrap; }
.chap-progress-mini { width: 44px; height: 4px; background: var(--border); border-radius: 99px; overflow: hidden; align-self: center; }
.chap-progress-mini > div { height: 100%; background: var(--ok); width: 0%; }
.sidebar-foot { border-top: 1px solid var(--border); padding: 14px 16px; }
.sf-row { display: flex; justify-content: space-between; font-size: 12.5px; color: var(--text-soft); font-weight: 600; margin-bottom: 6px; }
.sf-row strong { color: var(--brand); }
.sf-bar { height: 8px; border-radius: 99px; background: var(--border); overflow: hidden; }
.sf-bar > div { height: 100%; width: 0%; background: linear-gradient(90deg, var(--brand), var(--brand-2)); transition: width .4s; }
.sf-detail { font-size: 11.5px; color: var(--text-faint); margin-top: 6px; }
.search-empty { padding: 20px 14px; color: var(--text-faint); font-size: 13px; text-align: center; }
.backdrop { display: none; }

/* ============================ Nút & tiện ích ============================ */
.btn {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 10px 18px; border-radius: 11px; border: 1.5px solid transparent;
  font: inherit; font-weight: 700; font-size: 14px; cursor: pointer;
  transition: .15s; text-decoration: none !important;
}
.btn-primary { background: linear-gradient(135deg, var(--brand), var(--brand-2)); color: #fff; box-shadow: var(--shadow-sm); }
.btn-primary:hover { filter: brightness(1.07); }
.btn-ghost { background: var(--surface); color: var(--text); border-color: var(--border); }
.btn-ghost:hover { background: var(--surface-2); }
.btn-ok { background: var(--ok-soft); color: var(--ok); border-color: color-mix(in srgb, var(--ok) 35%, transparent); }
.btn-ok:hover { filter: brightness(1.04); }
.badge {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 3px 10px; border-radius: 999px;
  font-size: 12px; font-weight: 700; background: var(--brand-soft); color: var(--brand);
}
.badge.amber { background: color-mix(in srgb, var(--accent) 16%, transparent); color: color-mix(in srgb, var(--accent) 80%, var(--text)); }

/* ============================ Trang chủ ============================ */
.hero {
  position: relative; overflow: hidden;
  background:
    radial-gradient(900px 320px at 85% -40%, color-mix(in srgb, var(--brand) 22%, transparent), transparent),
    radial-gradient(600px 300px at -10% 110%, color-mix(in srgb, var(--brand-2) 16%, transparent), transparent),
    var(--surface);
  border: 1px solid var(--border); border-radius: 20px;
  padding: 44px 44px 40px; box-shadow: var(--shadow);
}
.hero-kicker { font-weight: 800; letter-spacing: 2.5px; text-transform: uppercase; font-size: 12px; color: var(--brand); margin-bottom: 12px; }
.hero h1 { margin: 0 0 14px; font-size: clamp(26px, 4vw, 40px); line-height: 1.2; font-weight: 800; }
.hero h1 em { font-style: normal; background: linear-gradient(120deg, var(--brand), var(--brand-2)); -webkit-background-clip: text; background-clip: text; color: transparent; }
.hero p.lead { font-size: 16.5px; color: var(--text-soft); max-width: 640px; margin: 0 0 24px; }
.hero-actions { display: flex; flex-wrap: wrap; gap: 12px; }
.hero-stats { display: flex; flex-wrap: wrap; gap: 14px; margin-top: 30px; }
.stat {
  flex: 1; min-width: 130px;
  background: var(--surface-2); border: 1px solid var(--border);
  border-radius: 14px; padding: 14px 18px;
}
.stat b { display: block; font-size: 24px; color: var(--brand); font-weight: 800; line-height: 1.2; }
.stat span { font-size: 12.5px; color: var(--text-soft); font-weight: 600; }

.section-title { display: flex; align-items: center; gap: 10px; margin: 40px 0 6px; font-size: 22px; font-weight: 800; }
.section-title .n { color: var(--brand); font-size: 14px; font-weight: 800; letter-spacing: 1.5px; }
.section-sub { color: var(--text-soft); margin: 0 0 20px; }

.chapter-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(285px, 1fr)); gap: 16px; }
.chapter-card {
  position: relative; display: flex; flex-direction: column; gap: 8px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 20px; box-shadow: var(--shadow-sm); transition: .18s; color: var(--text);
}
.chapter-card:hover { transform: translateY(-3px); box-shadow: var(--shadow); border-color: color-mix(in srgb, var(--brand) 40%, var(--border)); text-decoration: none; }
.chapter-card .cc-top { display: flex; align-items: center; gap: 10px; }
.chapter-card .cc-icon { font-size: 22px; width: 44px; height: 44px; display: grid; place-items: center; background: var(--brand-softer); border-radius: 12px; }
.chapter-card .cc-num { font-size: 11px; font-weight: 800; color: var(--brand); letter-spacing: 1.5px; text-transform: uppercase; }
.chapter-card h3 { margin: 0; font-size: 16.5px; font-weight: 700; line-height: 1.35; }
.chapter-card p { margin: 0; font-size: 13px; color: var(--text-soft); flex: 1; }
.chapter-card .cc-meta { display: flex; align-items: center; gap: 8px; font-size: 12px; color: var(--text-faint); font-weight: 600; }
.cc-progress { flex: 1; height: 5px; background: var(--border); border-radius: 99px; overflow: hidden; }
.cc-progress > div { height: 100%; background: var(--ok); border-radius: 99px; }

.info-cols { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 16px; }
.info-card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 22px 24px; box-shadow: var(--shadow-sm); }
.info-card h3 { margin: 0 0 8px; font-size: 16px; display: flex; gap: 8px; align-items: center; }
.info-card ul { margin: 0; padding-left: 20px; color: var(--text-soft); font-size: 14px; }
.info-card li { margin: 5px 0; }

/* ============================ Trang bài học ============================ */
.breadcrumb { display: flex; flex-wrap: wrap; gap: 6px; align-items: center; font-size: 13px; color: var(--text-faint); margin-bottom: 18px; font-weight: 600; }
.breadcrumb a { color: var(--text-faint); }
.breadcrumb a:hover { color: var(--brand); }
.lesson-header { margin-bottom: 6px; }
.lesson-chap-badge { margin-bottom: 10px; }
.lesson-header h1 { margin: 0 0 8px; font-size: clamp(23px, 3vw, 32px); line-height: 1.25; font-weight: 800; }
.lesson-meta { display: flex; flex-wrap: wrap; gap: 14px; font-size: 13px; color: var(--text-faint); font-weight: 600; margin-bottom: 22px; }

.lesson-body { font-size: 16px; }
.lesson-body h2 {
  margin: 38px 0 12px; font-size: 21px; font-weight: 800; line-height: 1.35;
  padding-bottom: 8px; border-bottom: 2px solid var(--brand-soft);
  scroll-margin-top: calc(var(--topbar-h) + 16px);
}
.lesson-body h3 { margin: 26px 0 8px; font-size: 17px; font-weight: 700; color: var(--text); scroll-margin-top: calc(var(--topbar-h) + 16px); }
.lesson-body p { margin: 10px 0; }
.lesson-body ul, .lesson-body ol { padding-left: 24px; margin: 10px 0; }
.lesson-body li { margin: 5px 0; }
.lesson-body strong { color: var(--text); }
.lesson-body hr { border: none; border-top: 1px dashed var(--border); margin: 30px 0; }

/* Bảng */
.tbl-wrap { overflow-x: auto; margin: 16px 0; border-radius: 12px; border: 1px solid var(--border); box-shadow: var(--shadow-sm); }
table.tbl { border-collapse: collapse; width: 100%; font-size: 14px; background: var(--surface); }
.tbl th, .tbl td { padding: 10px 14px; text-align: left; border-bottom: 1px solid var(--border); vertical-align: top; }
.tbl thead th { background: var(--brand-softer); color: var(--brand); font-weight: 800; font-size: 13px; letter-spacing: .3px; white-space: nowrap; }
.tbl tbody tr:last-child td { border-bottom: none; }
.tbl tbody tr:nth-child(even) { background: color-mix(in srgb, var(--surface-2) 55%, transparent); }

/* Code */
code {
  font-family: ui-monospace, "Cascadia Code", Consolas, monospace;
  background: var(--brand-softer); color: var(--brand);
  padding: 2px 7px; border-radius: 6px; font-size: .86em; font-weight: 600;
}
pre {
  background: var(--code-bg); color: var(--code-text);
  border-radius: 12px; padding: 18px 20px; overflow-x: auto;
  font-size: 13.5px; line-height: 1.65; margin: 16px 0;
}
pre code { background: none; color: inherit; padding: 0; font-weight: 400; }

/* Callout */
.callout {
  display: flex; gap: 12px; align-items: flex-start;
  border-radius: 12px; padding: 14px 18px; margin: 18px 0;
  border: 1px solid; font-size: 14.5px;
}
.callout .ci { font-size: 18px; line-height: 1.4; }
.callout.note { background: var(--brand-softer); border-color: color-mix(in srgb, var(--brand) 30%, transparent); }
.callout.tip { background: var(--ok-soft); border-color: color-mix(in srgb, var(--ok) 30%, transparent); }
.callout.warn { background: color-mix(in srgb, var(--accent) 10%, transparent); border-color: color-mix(in srgb, var(--accent) 40%, transparent); }
.callout p { margin: 0; }

/* Sơ đồ */
.diagram {
  margin: 20px 0; padding: 20px;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); box-shadow: var(--shadow-sm);
  text-align: center; overflow-x: auto;
}
.diagram svg { max-width: 560px; width: 100%; height: auto; }
.diagram-caption { margin-top: 10px; font-size: 12.5px; color: var(--text-faint); font-weight: 600; font-style: italic; }
.dgm-link { stroke: #94a8bf; stroke-width: 2; }
.dgm-link.hl { stroke: var(--brand); stroke-width: 2.5; }
.dgm-dash { stroke-dasharray: 6 5; }
.dgm-node { fill: var(--brand); }
.dgm-node.alt { fill: var(--brand-2); }
.dgm-node.warn { fill: var(--accent); }
.dgm-node.soft { fill: var(--ok); }
.dgm-label { font-size: 11px; fill: var(--text-soft); font-family: var(--font); font-weight: 600; }
.dgm-title { font-size: 12px; fill: var(--text); font-family: var(--font); font-weight: 700; }
.dgm-box { fill: var(--brand-softer); stroke: var(--brand); stroke-width: 1.6; rx: 7; }
.dgm-box.alt { fill: var(--surface-2); stroke: #94a8bf; }

/* Mục lục đầu bài */
.toc-box {
  background: var(--surface-2); border: 1px solid var(--border);
  border-radius: 12px; padding: 16px 20px; margin: 0 0 26px;
}
.toc-box b { display: block; font-size: 12.5px; text-transform: uppercase; letter-spacing: 1.5px; color: var(--text-faint); margin-bottom: 8px; }
.toc-box ul { list-style: none; margin: 0; padding: 0; columns: 2; column-gap: 28px; }
.toc-box li { margin: 3px 0; break-inside: avoid; }
.toc-box a { font-size: 13.5px; font-weight: 600; color: var(--text-soft); }
.toc-box a:hover { color: var(--brand); }

/* Thanh dưới bài học */
.lesson-actions {
  display: flex; flex-wrap: wrap; align-items: center; gap: 12px;
  margin: 40px 0 0; padding: 18px 20px;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); box-shadow: var(--shadow-sm);
}
.lesson-actions .grow { flex: 1; }
.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 18px; }
.pager a {
  display: flex; flex-direction: column; gap: 3px;
  border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--surface); padding: 14px 18px; box-shadow: var(--shadow-sm);
  color: var(--text); transition: .15s;
}
.pager a:hover { border-color: var(--brand); text-decoration: none; transform: translateY(-2px); }
.pager .plabel { font-size: 11.5px; font-weight: 800; letter-spacing: 1px; text-transform: uppercase; color: var(--text-faint); }
.pager .ptitle { font-weight: 700; font-size: 14.5px; color: var(--brand); }
.pager a.next { text-align: right; align-items: flex-end; }

/* ============================ Quiz ============================ */
.quiz-wrap { max-width: 780px; }
.quiz-head { margin-bottom: 24px; }
.quiz-head h1 { margin: 0 0 8px; font-size: 28px; font-weight: 800; }
.q-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 22px 24px; margin: 16px 0; box-shadow: var(--shadow-sm);
}
.q-num { font-size: 12px; font-weight: 800; color: var(--brand); letter-spacing: 1.5px; text-transform: uppercase; }
.q-text { font-size: 16.5px; font-weight: 700; margin: 6px 0 14px; }
.q-options { display: grid; gap: 8px; }
.q-opt {
  display: flex; align-items: center; gap: 10px; text-align: left;
  padding: 11px 16px; border-radius: 10px; cursor: pointer;
  border: 1.5px solid var(--border); background: var(--surface-2);
  font: inherit; font-size: 14.5px; color: var(--text); transition: .12s;
}
.q-opt:hover:not(:disabled) { border-color: var(--brand); background: var(--brand-softer); }
.q-opt .key {
  flex: none; width: 26px; height: 26px; border-radius: 8px;
  display: grid; place-items: center; font-weight: 800; font-size: 12.5px;
  background: var(--brand-soft); color: var(--brand);
}
.q-opt.correct { border-color: var(--ok); background: var(--ok-soft); }
.q-opt.correct .key { background: var(--ok); color: #fff; }
.q-opt.wrong { border-color: var(--bad); background: var(--bad-soft); }
.q-opt.wrong .key { background: var(--bad); color: #fff; }
.q-opt:disabled { cursor: default; opacity: .92; }
.q-explain { display: none; margin-top: 12px; padding: 12px 16px; border-radius: 10px; font-size: 13.5px; background: var(--brand-softer); border: 1px dashed color-mix(in srgb, var(--brand) 40%, transparent); color: var(--text-soft); }
.q-card.answered .q-explain { display: block; }
.quiz-result {
  position: sticky; bottom: 16px;
  background: var(--surface); border: 1.5px solid var(--brand);
  border-radius: var(--radius); padding: 18px 22px; margin-top: 22px;
  display: flex; align-items: center; gap: 16px; flex-wrap: wrap;
  box-shadow: var(--shadow); font-weight: 700;
}
.quiz-result .score { font-size: 22px; color: var(--brand); font-weight: 800; }

/* ============================ Toast ============================ */
.toast {
  position: fixed; bottom: 24px; left: 50%; transform: translateX(-50%) translateY(80px);
  background: var(--text); color: var(--bg);
  padding: 11px 20px; border-radius: 12px; font-weight: 700; font-size: 14px;
  box-shadow: var(--shadow); opacity: 0; transition: .3s; z-index: 99; pointer-events: none;
  display: flex; align-items: center; gap: 8px;
}
.toast.show { transform: translateX(-50%) translateY(0); opacity: 1; }

/* ============================ Footer ============================ */
.footer { border-top: 1px solid var(--border); background: var(--surface); margin-top: 40px; }
.footer-inner { max-width: 1080px; margin: 0 auto; padding: 26px 24px; font-size: 13.5px; color: var(--text-soft); display: flex; flex-direction: column; gap: 4px; }
.footer-note { color: var(--text-faint); font-size: 12.5px; }

/* ============================ 404 ============================ */
.nf { text-align: center; padding: 80px 0; }
.nf h1 { font-size: 60px; margin: 0; color: var(--brand); }
.nf p { color: var(--text-soft); }

/* ============================ Responsive ============================ */
@media (max-width: 1080px) {
  .topbar-links { display: none; }
}
@media (max-width: 900px) {
  .layout { grid-template-columns: 1fr; }
  .sidebar {
    position: fixed; z-index: 70; top: var(--topbar-h); bottom: 0; left: 0;
    width: min(88vw, 340px); transform: translateX(-102%);
    transition: transform .25s ease; box-shadow: var(--shadow);
  }
  body.sidebar-open .sidebar { transform: translateX(0); }
  .backdrop {
    display: block; position: fixed; inset: var(--topbar-h) 0 0 0; z-index: 65;
    background: rgba(9, 20, 35, .45); opacity: 0; pointer-events: none; transition: .25s;
  }
  body.sidebar-open .backdrop { opacity: 1; pointer-events: auto; }
  .main { padding: 24px 18px 70px; }
  .hero { padding: 30px 24px; }
  .toc-box ul { columns: 1; }
  .overall-pill .overall-bar { display: none; }
}
@media print {
  .topbar, .sidebar, .footer, .lesson-actions, .pager, .btn, .backdrop { display: none !important; }
  .layout { grid-template-columns: 1fr; }
  .main { max-width: 100%; padding: 0; }
}