/* 리버싱 웹북 디자인 시스템 v5 — 라이트/다크, 반응형, 인쇄 대응 */
:root {
  color-scheme: light;
  --bg: #ffffff;
  --surface: #ffffff;
  --surface-2: #f4f6fa;
  --ink: #1a1e28;
  --ink-2: #3d4354;
  --muted: #6b7280;
  --line: #e6e9f0;
  --line-2: #d4d9e4;
  --accent: #4338ca;
  --accent-ink: #3730a3;
  --accent-soft: #eef0fe;
  --ok: #15803d;
  --ok-soft: #e9f7ef;
  --warn-ink: #92400e;
  --warn-soft: #fff8ec;
  --warn-line: #ecd3a0;
  --deep-soft: #f6f8fb;
  --deep-line: #c3ccd9;
  --code-bg: #f6f8fa;
  --code-ink: #24292f;
  --code-head-bg: #eceff4;
  --code-head-ink: #57606a;
  --code-dot: #c4cad4;
  --inline-code: #eef1f6;
  --shadow: 0 1px 2px rgba(23, 26, 36, 0.05), 0 8px 24px -12px rgba(23, 26, 36, 0.18);
  --shadow-sm: 0 1px 2px rgba(23, 26, 36, 0.07);
  --r-lg: 14px;
  --r-md: 10px;
  --r-sm: 8px;
  --sidebar-w: 302px;
  --topbar-h: 60px;
  --font: "Pretendard", -apple-system, "Segoe UI", "Malgun Gothic", "Apple SD Gothic Neo", sans-serif;
  --mono: "D2Coding", Consolas, "Cascadia Code", monospace;
  --ease: cubic-bezier(0.2, 0.7, 0.3, 1);
}
[data-theme="dark"] {
  color-scheme: dark;
  --bg: #0e1120;
  --surface: #161a2e;
  --surface-2: #1e2440;
  --ink: #e8ebf5;
  --ink-2: #c3c9da;
  --muted: #8d94ab;
  --line: #262c48;
  --line-2: #333a5c;
  --accent: #8b85ff;
  --accent-ink: #c9c5ff;
  --accent-soft: #23264d;
  --ok: #4ade80;
  --ok-soft: #14291d;
  --warn-ink: #fbbf24;
  --warn-soft: #2c2313;
  --warn-line: #6b5320;
  --deep-soft: #1a1f38;
  --deep-line: #333a5c;
  --code-bg: #0a0d1d;
  --code-ink: #e6ebf7;
  --code-head-bg: #05070f;
  --code-head-ink: #9aa5c7;
  --code-dot: #3b4570;
  --inline-code: #232847;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.4), 0 10px 28px -12px rgba(0, 0, 0, 0.55);
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.4);
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation-duration: 0.001s !important; transition-duration: 0.001s !important; }
}
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font);
  line-height: 1.85;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  transition: background 0.25s var(--ease), color 0.25s var(--ease);
}
::selection { background: var(--accent-soft); }
a:focus-visible, button:focus-visible, input:focus-visible, [tabindex]:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
  border-radius: 4px;
}

/* ---------- 읽기 진행 바 ---------- */
.read-progress {
  position: fixed;
  top: 0;
  left: 0;
  height: 3px;
  width: 0;
  background: linear-gradient(90deg, var(--accent), #06b6d4);
  z-index: 100;
  border-radius: 0 3px 3px 0;
}

/* ---------- 상단 바 ---------- */
.topbar { display: none; }
body.has-chrome .topbar {
  display: flex;
  align-items: center;
  gap: 10px;
  position: fixed;
  top: 0;
  left: var(--sidebar-w);
  right: 0;
  height: var(--topbar-h);
  background: color-mix(in srgb, var(--surface) 88%, transparent);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--line);
  padding: 0 20px;
  z-index: 40;
}
.topbar .crumb { margin: 0; font-size: 13.5px; color: var(--muted); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.topbar .crumb a { color: var(--accent); text-decoration: none; }
.topbar .spacer { flex: 1; }
.icon-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 34px;
  height: 34px;
  padding: 0 8px;
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--ink-2);
  border-radius: var(--r-sm);
  font-size: 14px;
  cursor: pointer;
  transition: border-color 0.15s var(--ease), color 0.15s var(--ease), transform 0.1s var(--ease);
}
.icon-btn:hover { border-color: var(--accent); color: var(--accent); }
.icon-btn:active { transform: scale(0.94); }
.icon-btn svg { width: 17px; height: 17px; display: block; }
.topbar .menu-btn { display: none; }

/* ---------- 사이드바 ---------- */
.sidebar { display: none; }
body.has-chrome .sidebar {
  display: flex;
  flex-direction: column;
  position: fixed;
  top: 0;
  left: 0;
  bottom: 0;
  width: var(--sidebar-w);
  background: var(--surface);
  border-right: 1px solid var(--line);
  z-index: 50;
}
.sidebar .brand { padding: 20px 20px 6px; font-size: 17px; font-weight: 800; letter-spacing: -0.01em; }
.sidebar .brand a { color: inherit; text-decoration: none; }
.sidebar .brand small { display: block; font-size: 12px; font-weight: 400; color: var(--muted); margin-top: 2px; }
.sidebar .search { padding: 10px 16px 8px; position: relative; }
.sidebar .search input {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: var(--r-sm);
  padding: 9px 12px 9px 34px;
  font-size: 13px;
  font-family: inherit;
  color: var(--ink);
  background: var(--bg);
  outline: none;
  transition: border-color 0.15s var(--ease), box-shadow 0.15s var(--ease);
}
.sidebar .search input:focus { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
.sidebar .search .search-icon { position: absolute; left: 27px; top: 50%; transform: translateY(-58%); color: var(--muted); pointer-events: none; }
.sidebar .search .search-icon svg { width: 15px; height: 15px; display: block; }
.sidebar nav { flex: 1; overflow-y: auto; padding: 4px 10px 20px; scrollbar-width: thin; }
.sidebar nav a {
  display: flex;
  gap: 10px;
  align-items: flex-start;
  text-decoration: none;
  color: var(--ink);
  border-radius: var(--r-sm);
  padding: 8px 10px;
  transition: background 0.12s var(--ease);
}
.sidebar nav a:hover { background: var(--surface-2); }
.sidebar nav a.active { background: var(--accent-soft); }
.sidebar nav a.active .t { color: var(--accent-ink); font-weight: 700; }
.sidebar nav a .nicon { flex: none; width: 30px; height: 30px; border-radius: 8px; background: var(--surface-2); display: flex; align-items: center; justify-content: center; color: var(--muted); }
.sidebar nav a.active .nicon { background: var(--surface); color: var(--accent); }
.sidebar nav a .nicon svg { width: 16px; height: 16px; }
.sidebar nav a .tx { flex: 1; min-width: 0; }
.sidebar nav a .t { display: block; font-size: 13.5px; line-height: 1.45; }
.sidebar nav a .d { display: block; font-size: 11.5px; color: var(--muted); font-weight: 400; margin-top: 1px; }
.sidebar nav a .cnt { flex: none; font-size: 11px; color: var(--muted); background: var(--surface-2); border-radius: 20px; padding: 1px 8px; margin-top: 5px; }
.sidebar nav a .mini-progress { height: 3px; background: var(--line); border-radius: 2px; margin-top: 6px; overflow: hidden; }
.sidebar nav a .mini-progress i { display: block; height: 100%; width: 0; background: linear-gradient(90deg, var(--accent), #06b6d4); border-radius: 2px; transition: width 0.4s var(--ease); }
.sidebar .nav-group {
  font-size: 11.5px;
  font-weight: 800;
  color: var(--muted);
  padding: 16px 10px 6px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}
.sidebar .side-foot { padding: 12px 20px; border-top: 1px solid var(--line); font-size: 12px; color: var(--muted); }
.sidebar .side-foot a { color: var(--accent); text-decoration: none; }
.scrim { display: none; }

/* ---------- 본문 컨테이너 ---------- */
.book { max-width: 860px; margin: 28px auto 90px; padding: 0 22px; }
body.has-chrome nav.topnav { display: none; }
body.has-chrome .book {
  max-width: none;
  margin: 0;
  padding-top: calc(var(--topbar-h) + 30px);
  padding-bottom: 90px;
  padding-right: max(28px, calc((100% - var(--sidebar-w) - 800px) / 2));
  padding-left: max(28px, calc((100% - var(--sidebar-w) - 800px) / 2 + var(--sidebar-w)));
}
body.has-chrome aside.toc { display: none; }

/* ---------- 리프 (플랫 문서형) ---------- */
.leaf {
  background: transparent;
  border: none;
  border-top: 1px solid var(--line);
  border-radius: 0;
  box-shadow: none;
  padding: 30px 6px;
  margin: 0;
  scroll-margin-top: calc(var(--topbar-h) + 16px);
}
.leaf:first-of-type { border-top: none; }
.leaf-head { display: flex; align-items: center; gap: 12px; margin: 0 0 8px; }
.leaf-idx {
  flex: none;
  font-size: 12px;
  font-weight: 800;
  color: var(--accent-ink);
  background: var(--accent-soft);
  border-radius: 8px;
  padding: 3px 10px;
  letter-spacing: 0.02em;
}
.leaf-title { flex: 1; font-size: 21px; font-weight: 800; letter-spacing: -0.01em; margin: 0; line-height: 1.4; }
.leaf-toggle {
  flex: none;
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--muted);
  width: 30px;
  height: 30px;
  border-radius: 8px;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: transform 0.2s var(--ease), border-color 0.15s, color 0.15s;
}
.leaf-toggle:hover { border-color: var(--accent); color: var(--accent); }
.leaf-toggle svg { width: 15px; height: 15px; transition: transform 0.2s var(--ease); }
.leaf.collapsed .leaf-toggle svg { transform: rotate(-90deg); }
.leaf-body { display: grid; grid-template-rows: 1fr; transition: grid-template-rows 0.25s var(--ease), opacity 0.2s; }
.leaf-body > div { overflow: hidden; }
.leaf.collapsed .leaf-body { grid-template-rows: 0fr; opacity: 0; }
.leaf.reveal { animation: fadeUp 0.35s var(--ease) both; }
@keyframes fadeUp {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: none; }
}

/* ---------- 타이포 ---------- */
h1 { font-size: 32px; line-height: 1.35; margin: 0 0 10px; letter-spacing: -0.02em; }
h2 { font-size: 23px; margin: 44px 0 12px; padding-bottom: 8px; border-bottom: 1px solid var(--line); letter-spacing: -0.01em; scroll-margin-top: calc(var(--topbar-h) + 12px); }
h3 { font-size: 17.5px; margin: 28px 0 8px; scroll-margin-top: calc(var(--topbar-h) + 12px); }
.leaf h2:first-of-type { margin-top: 6px; }
p, li { font-size: 16px; }
a { color: var(--accent); }
a:hover { color: var(--accent-ink); }
.toc-anchor { opacity: 0; margin-left: 8px; text-decoration: none; font-size: 0.8em; transition: opacity 0.15s; }
h2:hover .toc-anchor, h3:hover .toc-anchor { opacity: 1; }
code {
  background: var(--inline-code);
  padding: 1px 7px;
  border-radius: 6px;
  font-size: 0.86em;
  font-family: var(--mono);
}
.code-wrap { position: relative; margin: 18px 0; border: 1px solid var(--line); border-radius: 10px; overflow: hidden; }
.code-head {
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--code-head-bg);
  color: var(--code-head-ink);
  font-size: 12px;
  padding: 8px 14px;
  border-bottom: 1px solid var(--line);
}
.code-head .dot { width: 9px; height: 9px; border-radius: 50%; background: var(--code-dot); }
.code-head .lang { margin-right: auto; letter-spacing: 0.04em; }
.copy-btn {
  border: 1px solid var(--line-2);
  background: var(--surface);
  color: var(--muted);
  border-radius: 6px;
  font-size: 12px;
  padding: 3px 10px;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  transition: border-color 0.15s, color 0.15s;
}
.copy-btn:hover { border-color: var(--accent); color: var(--accent); }
.copy-btn svg { width: 13px; height: 13px; }
.copy-btn.copied { border-color: var(--ok); color: var(--ok); }
pre {
  background: var(--code-bg);
  color: var(--code-ink);
  padding: 16px 18px;
  margin: 0;
  border-radius: 0 0 10px 10px;
  overflow-x: auto;
  font-size: 13.5px;
  line-height: 1.7;
  font-family: var(--mono);
}
pre code { background: none; padding: 0; color: inherit; }
pre:has(+ *) { margin-bottom: 0; }
.code-wrap:only-child pre, .code-wrap pre:only-of-type { border-radius: 10px; }
table { border-collapse: separate; border-spacing: 0; width: 100%; margin: 18px 0; font-size: 14px; border: 1px solid var(--line); border-radius: var(--r-md); overflow: hidden; }
th, td { padding: 10px 14px; text-align: left; border-bottom: 1px solid var(--line); }
tr:last-child th, tr:last-child td { border-bottom: none; }
th { background: var(--surface-2); font-size: 13px; color: var(--ink-2); }
tbody tr { transition: background 0.12s; }
tbody tr:hover { background: var(--accent-soft); }

/* ---------- 콜아웃 ---------- */
.note, .warn, .deep {
  position: relative;
  border-radius: var(--r-md);
  padding: 15px 18px 15px 52px;
  margin: 22px 0;
  font-size: 14.5px;
  border: 1px solid var(--line);
}
.note::before, .warn::before, .deep::before {
  content: "";
  position: absolute;
  left: 16px;
  top: 16px;
  width: 22px;
  height: 22px;
  background-size: contain;
  background-repeat: no-repeat;
  opacity: 0.9;
}
.note { background: var(--accent-soft); border-color: var(--line-2); }
.note strong { color: var(--accent-ink); }
.note::before { background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%234f46e5' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Ccircle cx='12' cy='12' r='10'/%3E%3Cpath d='M12 16v-4M12 8h.01'/%3E%3C/svg%3E"); }
.warn { background: var(--warn-soft); border-color: var(--warn-line); }
.warn strong { color: var(--warn-ink); }
.warn::before { background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%23b45309' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M10.3 3.9 1.8 18a2 2 0 0 0 1.7 3h17a2 2 0 0 0 1.7-3L13.7 3.9a2 2 0 0 0-3.4 0z'/%3E%3Cpath d='M12 9v4M12 17h.01'/%3E%3C/svg%3E"); }
.deep { background: var(--deep-soft); border-style: dashed; border-color: var(--deep-line); }
.deep::before { background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%2363667c' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Ccircle cx='12' cy='12' r='3'/%3E%3Cpath d='M2 12s3.5-7 10-7 10 7 10 7-3.5 7-10 7-10-7-10-7z'/%3E%3C/svg%3E"); }

/* ---------- 그림 ---------- */
.fig { margin: 22px 0; border: 1px solid var(--line); border-radius: var(--r-md); background: var(--surface); padding: 18px; overflow-x: auto; }
.fig img { display: block; max-width: 100%; height: auto; margin: 0 auto; }
.fig figcaption { margin-top: 12px; font-size: 13px; color: var(--muted); text-align: center; line-height: 1.6; }

/* ---------- 단원 내비게이션 (단원별 1페이지) ---------- */
.leaf-nav {
  display: flex;
  align-items: center;
  gap: 8px;
  margin: 0 0 18px;
  flex-wrap: wrap;
}
.lnav-btn {
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--ink-2);
  border-radius: var(--r-sm);
  font-size: 13.5px;
  font-family: inherit;
  padding: 8px 14px;
  cursor: pointer;
  text-decoration: none;
  transition: border-color 0.15s var(--ease), color 0.15s var(--ease);
  white-space: nowrap;
}
a.lnav-btn { display: inline-block; }
.lnav-btn:hover:not(:disabled) { border-color: var(--accent); color: var(--accent); }
.lnav-btn:disabled { opacity: 0.4; cursor: default; }
.leaf-select {
  flex: 1;
  min-width: 180px;
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--ink);
  border-radius: var(--r-sm);
  font-size: 13.5px;
  font-family: inherit;
  padding: 8px 12px;
  cursor: pointer;
  outline: none;
}
.leaf-select:focus { border-color: var(--accent); }

/* ---------- 단원 목차 카드 ---------- */
.leaf-cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 10px; margin: 20px 0 8px; }
.lcard {
  display: flex;
  align-items: center;
  gap: 10px;
  border: 1px solid var(--line);
  background: var(--surface);
  border-radius: var(--r-md);
  padding: 12px 14px;
  text-decoration: none;
  color: inherit;
  transition: border-color 0.15s var(--ease);
}
.lcard:hover { border-color: var(--accent); }
.lcard .ln {
  flex: none;
  font-size: 12px;
  font-weight: 800;
  color: var(--accent-ink);
  background: var(--accent-soft);
  border-radius: 7px;
  padding: 2px 8px;
}
.lcard .lt { flex: 1; font-size: 13.5px; line-height: 1.5; min-width: 0; }
.lcard .lbar { flex: none; width: 56px; height: 5px; background: var(--line); border-radius: 3px; overflow: hidden; }
.lcard .lbar i { display: block; height: 100%; width: 0; background: linear-gradient(90deg, var(--accent), #06b6d4); border-radius: 3px; }
.lcard .lpct { flex: none; font-size: 11.5px; color: var(--muted); }
.lcard .qpass { flex: none; font-size: 11.5px; font-weight: 800; color: var(--ok); }

/* ---------- 공식 랩·과제 ---------- */
.lab-block { margin-top: 40px; }
.lab-item {
  border: 1px solid var(--line);
  border-left: 3px solid var(--accent);
  border-radius: var(--r-md);
  background: var(--surface);
  padding: 16px 20px;
  margin: 0 0 14px;
}
.lab-head { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; margin-bottom: 4px; }
.lab-head strong { font-size: 16px; }
.lab-source { font-size: 13px; color: var(--muted); margin-bottom: 6px; }
.lab-item p { font-size: 14.5px; margin: 6px 0; }
.lab-item ul { margin: 8px 0 4px; padding-left: 20px; font-size: 14px; }
.lab-item ul li { margin-bottom: 4px; }

/* ---------- 체크포인트 (인터랙티브) ---------- */
.check { list-style: none; margin: 14px 0 4px; padding: 0; }
.check li {
  position: relative;
  margin: 0 0 8px;
  padding: 10px 14px 10px 44px;
  border: 1px solid var(--line);
  border-radius: var(--r-sm);
  background: var(--surface);
  cursor: pointer;
  transition: border-color 0.15s var(--ease), background 0.15s var(--ease);
  font-size: 14.5px;
}
.check li:hover { border-color: var(--accent); }
.check li::before {
  content: "";
  position: absolute;
  left: 14px;
  top: 50%;
  transform: translateY(-50%);
  width: 18px;
  height: 18px;
  border-radius: 6px;
  border: 2px solid var(--line-2);
  background: var(--surface);
  transition: background 0.15s var(--ease), border-color 0.15s var(--ease);
}
.check li.done { color: var(--muted); text-decoration: line-through; background: var(--surface-2); }
.check li.done::before {
  border-color: var(--ok);
  background: var(--ok) url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='white' stroke-width='3.5' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M20 6 9 17l-5-5'/%3E%3C/svg%3E") center/12px no-repeat;
}
.check-progress { display: flex; align-items: center; gap: 10px; margin: 10px 0 4px; font-size: 13px; color: var(--muted); }
.check-progress .bar { flex: 1; height: 6px; background: var(--line); border-radius: 4px; overflow: hidden; }
.check-progress .bar i { display: block; height: 100%; width: 0; background: linear-gradient(90deg, var(--accent), #06b6d4); border-radius: 4px; transition: width 0.35s var(--ease); }

.crumb { font-size: 13px; color: var(--muted); margin-bottom: 6px; }
.crumb a { color: var(--accent); text-decoration: none; }
.muted { color: var(--muted); font-size: 13.5px; }
.kbd {
  display: inline-block;
  border: 1px solid var(--line-2);
  border-bottom-width: 2px;
  border-radius: 6px;
  padding: 0 7px;
  font-size: 12.5px;
  font-family: var(--mono);
  background: var(--surface);
}
.pill {
  display: inline-block;
  font-size: 12px;
  font-weight: 700;
  border-radius: 20px;
  padding: 2px 12px;
  background: var(--accent-soft);
  color: var(--accent-ink);
}

/* ---------- 이전/다음 카드 ---------- */
.pagenav { display: flex; gap: 12px; margin-top: 40px; }
.pagenav a, .pagenav span {
  flex: 1;
  border: 1px solid var(--line);
  background: var(--surface);
  border-radius: var(--r-md);
  padding: 16px 20px;
  font-size: 14px;
  color: var(--ink);
  text-decoration: none;
  transition: border-color 0.15s var(--ease), transform 0.15s var(--ease), box-shadow 0.15s var(--ease);
}
.pagenav a:hover { border-color: var(--accent); transform: translateY(-2px); box-shadow: var(--shadow); }
.pagenav span { visibility: hidden; }
.pagenav a:last-child { text-align: right; }
.pagenav .dir { display: block; font-size: 12px; color: var(--muted); margin-bottom: 2px; }

/* ---------- 우측 미니 목차 ---------- */
.page-toc { display: none; }
@media (min-width: 1640px) {
  body.has-chrome .page-toc {
    display: block;
    position: fixed;
    top: calc(var(--topbar-h) + 24px);
    right: max(20px, calc((100% - 1500px) / 2));
    width: 215px;
    font-size: 12.5px;
    max-height: calc(100vh - var(--topbar-h) - 60px);
    overflow-y: auto;
    scrollbar-width: thin;
  }
  .page-toc h2 { font-size: 11px; border: none; margin: 0 0 6px; padding: 0; color: var(--muted); text-transform: uppercase; letter-spacing: 0.06em; }
  .page-toc ul { list-style: none; margin: 0; padding: 0; }
  .page-toc li { margin: 2px 0; line-height: 1.5; }
  .page-toc li.sub { padding-left: 13px; }
  .page-toc a { color: var(--muted); text-decoration: none; display: block; border-left: 2px solid var(--line); padding-left: 10px; transition: color 0.12s, border-color 0.12s; }
  .page-toc a:hover { color: var(--ink); }
  .page-toc a.on { color: var(--accent-ink); font-weight: 700; border-left-color: var(--accent); }
  .page-toc .toc-tools { display: flex; gap: 6px; margin-top: 12px; }
  .page-toc .toc-tools button {
    flex: 1; font-size: 11.5px; padding: 5px 0; border: 1px solid var(--line);
    background: var(--surface); color: var(--muted); border-radius: 6px; cursor: pointer;
  }
  .page-toc .toc-tools button:hover { color: var(--accent); border-color: var(--accent); }
}

/* ---------- 구형 topnav (no-JS 폴백) ---------- */
.topnav { background: #141829; color: #e5e7eb; padding: 10px 20px; font-size: 14px; position: sticky; top: 0; z-index: 30; }
.topnav a { color: #93c5fd; text-decoration: none; margin-right: 14px; }
.topnav b { margin-right: 16px; }

/* ---------- 히어로 · 카드 (index) ---------- */
.hero {
  position: relative;
  border-radius: var(--r-lg);
  padding: 42px 40px;
  margin: 26px 0 28px;
  color: var(--ink);
  background: var(--surface);
  border: 1px solid var(--line);
  border-top: 3px solid var(--accent);
}
.hero h1 { font-size: 32px; margin: 0 0 10px; }
.hero h1 .accent-bar { color: var(--accent); }
.hero p { color: var(--ink-2); font-size: 15.5px; max-width: 660px; margin: 0 0 22px; }
.hero .cta-row { display: flex; gap: 10px; flex-wrap: wrap; }
.hero::after { display: none; }
.hero h1 { font-size: 32px; margin: 0 0 10px; position: static; }
.hero p { position: static; color: var(--ink-2); font-size: 15.5px; max-width: 660px; margin: 0 0 22px; }
.hero .cta-row { position: static; display: flex; gap: 10px; flex-wrap: wrap; }
.hero-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  border-radius: 10px;
  padding: 11px 22px;
  font-size: 14.5px;
  font-weight: 800;
  text-decoration: none;
  transition: transform 0.15s var(--ease), box-shadow 0.15s var(--ease);
}
.hero-btn.primary { background: var(--accent); color: #fff; }
.hero-btn.primary:hover { transform: translateY(-1px); box-shadow: 0 8px 18px -8px var(--accent); color: #fff; }
.hero-btn.ghost { border: 1px solid var(--line-2); color: var(--ink); background: var(--surface); }
.hero-btn.ghost:hover { border-color: var(--accent); color: var(--accent); }
.hero-btn svg { width: 16px; height: 16px; }
.stats { display: flex; gap: 12px; flex-wrap: wrap; margin: 0 0 30px; }
.stat {
  flex: 1;
  min-width: 150px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--r-md);
  padding: 14px 18px;
}
.stat b { display: block; font-size: 24px; letter-spacing: -0.02em; }
.stat span { font-size: 12.5px; color: var(--muted); }
.track-title { display: flex; align-items: center; gap: 10px; margin: 38px 0 4px; }
.track-title .ticon { width: 34px; height: 34px; border-radius: 10px; background: var(--accent-soft); color: var(--accent); display: flex; align-items: center; justify-content: center; }
.track-title .ticon svg { width: 18px; height: 18px; }
.track-title h2 { margin: 0; padding: 0; border: none; font-size: 21px; }
.cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(250px, 1fr)); gap: 14px; margin: 16px 0 8px; }
.card {
  display: flex;
  flex-direction: column;
  gap: 8px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--r-lg);
  padding: 20px;
  text-decoration: none;
  color: inherit;
  transition: border-color 0.15s var(--ease), background 0.15s var(--ease);
  animation: fadeUp 0.4s var(--ease) both;
}
.card:hover { border-color: var(--accent); }
.card:hover .cicon { background: var(--accent); color: #fff; }
.card .cicon { transition: background 0.15s var(--ease), color 0.15s var(--ease); }
.card .cicon { width: 40px; height: 40px; border-radius: 12px; background: var(--accent-soft); color: var(--accent); display: flex; align-items: center; justify-content: center; }
.card .cicon svg { width: 21px; height: 21px; }
.card h3 { margin: 0; font-size: 16.5px; }
.card p { margin: 0; font-size: 13.5px; color: var(--muted); line-height: 1.6; flex: 1; }
.card .meta { display: flex; align-items: center; gap: 8px; font-size: 12px; color: var(--muted); }
.card .bar { height: 5px; background: var(--line); border-radius: 3px; overflow: hidden; }
.card .bar i { display: block; height: 100%; width: 0; background: linear-gradient(90deg, var(--accent), #06b6d4); border-radius: 3px; transition: width 0.5s var(--ease); }
.timeline { list-style: none; margin: 14px 0; padding: 0; counter-reset: step; }
.timeline li { position: relative; padding: 0 0 18px 42px; font-size: 14.5px; }
.timeline li::before {
  counter-increment: step;
  content: counter(step);
  position: absolute;
  left: 0;
  top: 2px;
  width: 26px;
  height: 26px;
  border-radius: 50%;
  background: var(--accent-soft);
  color: var(--accent-ink);
  font-size: 13px;
  font-weight: 800;
  display: flex;
  align-items: center;
  justify-content: center;
}
.timeline li::after { content: ""; position: absolute; left: 12.5px; top: 32px; bottom: 0; width: 2px; background: var(--line); }
.timeline li:last-child::after { display: none; }

/* ---------- 스켈레톤 로딩 ---------- */
.skeleton { display: flex; flex-direction: column; gap: 14px; margin-top: 8px; }
.skeleton i {
  display: block;
  height: 16px;
  border-radius: 8px;
  background: linear-gradient(90deg, var(--line) 25%, var(--surface-2) 50%, var(--line) 75%);
  background-size: 200% 100%;
  animation: shimmer 1.2s infinite linear;
}
@keyframes shimmer { from { background-position: 200% 0; } to { background-position: -200% 0; } }

/* ---------- 검색 결과 ---------- */
.search-results { padding: 6px 4px 16px; }
.search-results .sr-group { font-size: 11.5px; font-weight: 800; color: var(--muted); text-transform: uppercase; letter-spacing: 0.06em; padding: 10px 8px 2px; }
.search-results a { padding: 7px 8px; }
.search-empty { padding: 16px 10px; font-size: 13px; color: var(--muted); }

/* ---------- 토스트 ---------- */
.toast {
  position: fixed;
  bottom: 26px;
  left: 50%;
  transform: translateX(-50%) translateY(20px);
  background: var(--ink);
  color: var(--bg);
  font-size: 13.5px;
  padding: 10px 20px;
  border-radius: 24px;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.25s var(--ease), transform 0.25s var(--ease);
  z-index: 200;
}
.toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }

/* ---------- 퀴즈 ---------- */
.quiz { margin-top: 40px; border-top: 2px solid var(--line); padding-top: 8px; }
.quiz-toolbar { display: flex; align-items: center; gap: 10px; margin: 16px 0 20px; flex-wrap: wrap; }
.btn { border-radius: var(--r-sm); padding: 10px 22px; font-size: 14px; font-weight: 700; cursor: pointer; font-family: inherit; transition: transform 0.1s, box-shadow 0.15s, background 0.15s; }
.btn:active { transform: scale(0.97); }
.btn-primary { background: var(--accent); color: #fff; border: 1px solid var(--accent); }
.btn-primary:hover { box-shadow: 0 6px 16px -6px var(--accent); }
.btn-ghost { background: var(--surface); color: var(--ink); border: 1px solid var(--line); }
.btn-ghost:hover { border-color: var(--accent); color: var(--accent); }
.quiz-score { font-size: 15px; font-weight: 800; margin-left: 6px; }
.quiz-list { margin: 0; padding: 0; list-style: none; counter-reset: quiz; }
.quiz-item { counter-increment: quiz; border: 1px solid var(--line); background: var(--surface); border-radius: var(--r-md); padding: 18px 20px; margin: 0 0 14px; transition: border-color 0.2s, background 0.2s; }
.quiz-item::before { content: "Q" counter(quiz) "."; font-weight: 800; font-size: 13px; color: var(--muted); }
.quiz-q { font-weight: 700; font-size: 15.5px; margin: 6px 0 12px; }
.quiz-choices { display: grid; gap: 8px; }
.quiz-choice { display: flex; gap: 10px; align-items: flex-start; border: 1px solid var(--line); border-radius: var(--r-sm); padding: 10px 13px; font-size: 14.5px; cursor: pointer; transition: border-color 0.12s, background 0.12s, transform 0.1s; }
.quiz-choice:hover { border-color: var(--accent); transform: translateX(2px); }
.quiz-choice input { margin-top: 4px; accent-color: var(--accent); }
.quiz-item.is-correct { border-color: var(--ok); background: var(--ok-soft); }
.quiz-item.is-wrong { border-color: #e03131; }
.quiz-choice.is-answer { border-color: var(--ok); background: var(--ok-soft); font-weight: 700; }
.quiz-choice.is-picked:not(.is-answer) { border-color: #e03131; background: rgba(224, 49, 49, 0.08); }
.quiz-explain { margin-top: 12px; font-size: 14px; background: var(--surface-2); border: 1px solid var(--line); border-radius: var(--r-sm); padding: 10px 14px; }

/* ---------- 구형 단원 뱃지 등 잔여 ---------- */
.unit { display: flex; align-items: center; gap: 10px; }
.unit-no { background: #111827; color: #fff; font-size: 12px; font-weight: 700; border-radius: 6px; padding: 3px 10px; white-space: nowrap; }
[data-theme="dark"] .unit-no { background: #e8ebf5; color: #111827; }
.progress { height: 3px; background: var(--line); border-radius: 2px; margin: 0 0 18px; }
.progress i { display: block; height: 100%; background: var(--accent); border-radius: 2px; }

/* ---------- 반응형 ---------- */
@media (max-width: 1024px) {
  body.has-chrome .sidebar { transform: translateX(-105%); transition: transform 0.22s var(--ease); box-shadow: none; }
  body.has-chrome.sidebar-open .sidebar { transform: none; box-shadow: 0 0 60px rgba(0, 0, 0, 0.25); }
  body.has-chrome.sidebar-open .scrim { display: block; position: fixed; inset: 0; background: rgba(10, 12, 24, 0.45); z-index: 45; }
  body.has-chrome .topbar { left: 0; }
  body.has-chrome .topbar .menu-btn { display: inline-flex; }
  body.has-chrome .book { padding-left: 18px; padding-right: 18px; }
  .leaf { padding: 22px 20px; }
  .hero { padding: 34px 26px; }
  .hero h1 { font-size: 26px; }
}
/* ---------- 모바일 (≤720px) ---------- */
@media (max-width: 720px) {
  .topnav {
    padding: 8px 12px;
    font-size: 13px;
    white-space: nowrap;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
  }
  .topnav::-webkit-scrollbar { display: none; }
  .topnav a { margin-right: 10px; }
  .topnav b { margin-right: 12px; }
  body.has-chrome .book {
    padding-top: calc(var(--topbar-h) + 18px);
    padding-left: max(14px, env(safe-area-inset-left, 0px));
    padding-right: max(14px, env(safe-area-inset-right, 0px));
  }
  body.has-chrome .topbar {
    padding-left: max(12px, env(safe-area-inset-left, 0px));
    padding-right: max(12px, env(safe-area-inset-right, 0px));
  }
  body.has-chrome .sidebar { width: min(86vw, var(--sidebar-w)); }
  .leaf { padding: 20px 2px; }
  .leaf-title { font-size: 18.5px; }
  .leaf-idx { font-size: 11px; padding: 2px 8px; }
  h1 { font-size: 25px; }
  h2 { font-size: 20px; margin: 32px 0 10px; }
  h3 { font-size: 16.5px; margin: 22px 0 6px; }
  p, li { font-size: 15.5px; }
  pre { font-size: 12.5px; padding: 13px 14px; }
  table { display: block; width: 100%; overflow-x: auto; -webkit-overflow-scrolling: touch; white-space: nowrap; }
  th, td { padding: 8px 10px; font-size: 13px; }
  .note, .warn, .deep { padding: 13px 14px 13px 44px; font-size: 14px; }
  .note::before, .warn::before, .deep::before { left: 12px; top: 14px; width: 20px; height: 20px; }
  .leaf-cards, .cards { grid-template-columns: 1fr; }
  .pagenav { flex-direction: column; }
  .pagenav a, .pagenav span { padding: 12px 16px; }
  .pagenav a:last-child { text-align: left; }
  .hero { padding: 26px 20px; margin: 16px 0 20px; }
  .hero h1 { font-size: 23px; }
  .hero p { font-size: 14.5px; }
  .stat { min-width: 120px; padding: 12px 14px; }
  .stat b { font-size: 20px; }
  .quiz-item { padding: 14px; }
  .quiz-choice { padding: 9px 11px; font-size: 14px; }
  .lab-item { padding: 13px 16px; }
  .lnav-btn { padding: 7px 11px; font-size: 13px; }
  .leaf-select { min-width: 120px; }
  .toast { bottom: 16px; max-width: calc(100vw - 24px); }
}
@media (max-width: 420px) {
  .leaf { padding: 16px 0; }
  .leaf-title { font-size: 17.5px; }
  h1 { font-size: 22px; }
  .topbar { padding: 0 12px; }
  .pagenav span { display: none; }
}

/* ---------- 인쇄 ---------- */
@media print {
  .sidebar, .topbar, .page-toc, .read-progress, .scrim, .leaf-toggle, .copy-btn, .quiz-toolbar, .toc-tools { display: none !important; }
  body.has-chrome .book { padding: 0; }
  .leaf { box-shadow: none; break-inside: avoid; }
  .leaf.collapsed .leaf-body { grid-template-rows: 1fr; opacity: 1; }
  .leaf.collapsed .leaf-body > div { overflow: visible; }
  .hero { -webkit-print-color-adjust: exact; print-color-adjust: exact; }
  pre, table { break-inside: avoid; }
}