/* ============================================================
   Book layout — PC 3-column / Mobile 1-column
   ============================================================ */

/* ---- Site header (mobile + toolbar) ---- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  height: var(--header-h);
  padding: 0 0.75rem;
  background: var(--navy-deep);
  color: #fff;
  box-shadow: var(--shadow);
}

.site-header a {
  color: #fff;
  text-decoration: none;
}

.site-header a:hover {
  color: #c5d8f0;
  text-decoration: none;
}

.header-brand {
  font-weight: 700;
  font-size: 0.95rem;
  letter-spacing: -0.02em;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  flex: 1;
  min-width: 0;
}

.header-brand span {
  opacity: 0.7;
  font-weight: 500;
  font-size: 0.8rem;
  margin-left: 0.35rem;
}

.menu-toggle {
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 4px;
  width: 36px;
  height: 36px;
  padding: 8px;
  border-radius: var(--radius-sm);
  flex-shrink: 0;
}

.menu-toggle:hover,
.menu-toggle:focus-visible {
  background: rgba(255, 255, 255, 0.12);
}

.menu-toggle span {
  display: block;
  height: 2px;
  background: #fff;
  border-radius: 1px;
  transition: transform var(--dur) var(--ease);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 0.2rem;
  flex-shrink: 0;
}

.icon-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 34px;
  height: 34px;
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  color: #fff;
  opacity: 0.9;
}

.icon-btn:hover,
.icon-btn:focus-visible {
  background: rgba(255, 255, 255, 0.12);
  opacity: 1;
}

.icon-btn[aria-pressed="true"] {
  background: rgba(255, 255, 255, 0.2);
}

/* ---- Layout shell ---- */
.book-shell {
  display: grid;
  grid-template-columns: 1fr;
  min-height: calc(100vh - var(--header-h));
}

/* Sidebar (TOC) */
.sidebar {
  position: fixed;
  top: var(--header-h);
  left: 0;
  bottom: 0;
  width: min(86vw, 300px);
  z-index: 90;
  background: var(--surface);
  border-right: 1px solid var(--border);
  overflow-y: auto;
  overscroll-behavior: contain;
  transform: translateX(-100%);
  transition: transform var(--dur) var(--ease);
  padding: 0.75rem 0 2rem;
}

.sidebar.is-open {
  transform: translateX(0);
  box-shadow: var(--shadow-md);
}

.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  top: var(--header-h);
  z-index: 85;
  background: rgba(10, 26, 46, 0.45);
}

.sidebar-overlay.is-visible {
  display: block;
}

.sidebar-title {
  padding: 0.4rem 1rem 0.6rem;
  font-size: var(--fs-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-muted);
  border-bottom: 1px solid var(--border-light);
  margin-bottom: 0.4rem;
}

.toc-era {
  margin-bottom: 0.35rem;
}

.toc-era-btn {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  padding: 0.4rem 1rem;
  font-size: var(--fs-sm);
  font-weight: 700;
  color: var(--navy);
  text-align: left;
}

.toc-era-btn:hover {
  background: var(--blue-pale);
}

.toc-era-btn .chevron {
  font-size: 0.65rem;
  opacity: 0.6;
  transition: transform var(--dur) var(--ease);
}

.toc-era.is-collapsed .toc-era-list {
  display: none;
}

.toc-era.is-collapsed .chevron {
  transform: rotate(-90deg);
}

.toc-era-list {
  list-style: none;
  padding: 0;
}

.toc-era-list a {
  display: flex;
  align-items: flex-start;
  gap: 0.4rem;
  padding: 0.35rem 1rem 0.35rem 1.25rem;
  font-size: var(--fs-sm);
  color: var(--text-secondary);
  text-decoration: none;
  line-height: 1.35;
  border-left: 3px solid transparent;
}

.toc-era-list a:hover {
  background: var(--blue-pale);
  color: var(--blue);
  text-decoration: none;
}

.toc-era-list a.is-active {
  background: var(--blue-pale);
  color: var(--blue);
  font-weight: 600;
  border-left-color: var(--blue);
}

.toc-era-list a.is-read::after {
  content: "✓";
  margin-left: auto;
  color: var(--tip-border);
  font-size: 0.7rem;
  flex-shrink: 0;
}

.toc-num {
  color: var(--text-muted);
  font-size: var(--fs-xs);
  font-variant-numeric: tabular-nums;
  min-width: 1.6em;
  flex-shrink: 0;
}

/* Main content */
.main-wrap {
  min-width: 0;
  padding: 1rem 1rem 3rem;
}

.main-content {
  max-width: var(--content-max);
  margin: 0 auto;
}

/* Right aside (PC) */
.aside-panel {
  display: none;
}

/* ---- Cover / home ---- */
.cover {
  background: linear-gradient(145deg, var(--navy-deep) 0%, var(--navy-soft) 55%, #1e4a6e 100%);
  color: #fff;
  padding: 2.5rem 1.25rem 2rem;
  margin: -1rem -1rem 1.5rem;
  position: relative;
  overflow: hidden;
}

.cover::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 80% 60% at 90% 10%, rgba(53, 132, 228, 0.25), transparent),
    radial-gradient(ellipse 50% 40% at 10% 90%, rgba(15, 39, 68, 0.4), transparent);
  pointer-events: none;
}

.cover-inner {
  position: relative;
  max-width: var(--content-max);
  margin: 0 auto;
}

.cover-badge {
  display: inline-block;
  font-size: var(--fs-xs);
  font-weight: 600;
  letter-spacing: 0.04em;
  opacity: 0.85;
  margin-bottom: 0.6rem;
  border: 1px solid rgba(255, 255, 255, 0.35);
  padding: 0.2rem 0.55rem;
  border-radius: 2px;
}

.cover h1 {
  color: #fff;
  font-size: clamp(1.75rem, 5vw, 2.4rem);
  font-weight: 800;
  letter-spacing: -0.03em;
  margin-bottom: 0.5rem;
  line-height: 1.25;
}

.cover-sub {
  font-size: var(--fs-lg);
  opacity: 0.9;
  margin-bottom: 1.25rem;
  max-width: 28em;
}

.cover-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem 1.25rem;
  font-size: var(--fs-sm);
  opacity: 0.8;
}

.cover-cta {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  margin-top: 1.25rem;
  padding: 0.6rem 1.2rem;
  background: #fff;
  color: var(--navy-deep);
  font-weight: 700;
  font-size: var(--fs-sm);
  border-radius: var(--radius);
  text-decoration: none;
  transition: transform var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}

.cover-cta:hover {
  transform: translateY(-1px);
  box-shadow: 0 4px 14px rgba(0, 0, 0, 0.2);
  color: var(--navy-deep);
  text-decoration: none;
}

/* Era entry cards */
.era-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.75rem;
  margin: 1rem 0 2rem;
}

.era-card {
  display: block;
  padding: 1rem 1.1rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-left: 4px solid var(--blue);
  border-radius: var(--radius);
  text-decoration: none;
  color: inherit;
  transition: border-color var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}

.era-card:hover {
  border-color: var(--blue);
  box-shadow: var(--shadow);
  text-decoration: none;
  color: inherit;
}

.era-card h3 {
  margin: 0 0 0.25rem;
  font-size: var(--fs-lg);
  color: var(--navy);
}

.era-card p {
  margin: 0;
  font-size: var(--fs-sm);
  color: var(--text-muted);
}

.era-card .era-meta {
  margin-top: 0.5rem;
  font-size: var(--fs-xs);
  color: var(--blue);
  font-weight: 600;
}

/* Home TOC list */
.home-toc {
  margin: 1rem 0 2rem;
}

.home-toc-era {
  margin-bottom: 1.25rem;
}

.home-toc-era h3 {
  font-size: var(--fs-lg);
  margin: 0 0 0.4rem;
  padding-bottom: 0.3rem;
  border-bottom: 2px solid var(--blue-muted);
}

.home-toc-era ol {
  list-style: none;
  padding: 0;
  columns: 1;
  gap: 1.5rem;
}

.home-toc-era li {
  margin: 0;
  padding: 0.2rem 0;
  font-size: var(--fs-sm);
  break-inside: avoid;
}

.home-toc-era a {
  color: var(--text-secondary);
  text-decoration: none;
}

.home-toc-era a:hover {
  color: var(--blue);
  text-decoration: underline;
}

.home-toc-era .toc-num {
  display: inline-block;
  min-width: 2em;
  color: var(--text-muted);
  font-variant-numeric: tabular-nums;
}

section.page-section {
  margin-bottom: 2rem;
}

section.page-section > h2 {
  font-size: var(--fs-xl);
  color: var(--navy);
  border-bottom: 2px solid var(--navy);
  padding-bottom: 0.35rem;
  margin-bottom: 0.75rem;
}

/* Back to top */
.back-to-top {
  position: fixed;
  right: 1rem;
  bottom: 1rem;
  z-index: 50;
  width: 42px;
  height: 42px;
  border-radius: 50%;
  background: var(--navy-deep);
  color: #fff;
  font-size: 1.1rem;
  box-shadow: var(--shadow-md);
  opacity: 0;
  visibility: hidden;
  transform: translateY(8px);
  transition: opacity var(--dur) var(--ease), transform var(--dur) var(--ease),
    visibility var(--dur);
}

.back-to-top.is-visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-to-top:hover {
  background: var(--navy-soft);
}

/* Search panel */
.search-panel {
  display: none;
  position: fixed;
  top: var(--header-h);
  left: 0;
  right: 0;
  z-index: 95;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 0.75rem 1rem 1rem;
  box-shadow: var(--shadow-md);
  max-height: min(70vh, 480px);
  overflow: auto;
}

.search-panel.is-open {
  display: block;
}

.search-input-wrap {
  display: flex;
  gap: 0.5rem;
  max-width: 560px;
  margin: 0 auto 0.75rem;
}

.search-input-wrap input {
  flex: 1;
  padding: 0.55rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: 1rem;
  background: var(--bg);
  color: var(--text);
}

.search-input-wrap input:focus {
  outline: 2px solid var(--blue-light);
  outline-offset: 1px;
}

.search-close {
  flex-shrink: 0;
  width: auto !important;
  padding: 0 0.65rem;
  color: var(--text) !important;
  font-size: var(--fs-sm);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  height: 38px;
}

.search-close:hover {
  background: var(--blue-pale) !important;
}

.search-results {
  max-width: 560px;
  margin: 0 auto;
  list-style: none;
  padding: 0;
}

.search-results li {
  margin: 0;
  border-bottom: 1px solid var(--border-light);
}

.search-results a {
  display: block;
  padding: 0.55rem 0.25rem;
  text-decoration: none;
  color: var(--text);
}

.search-results a:hover {
  background: var(--blue-pale);
}

.search-results .result-title {
  font-weight: 600;
  color: var(--blue);
  font-size: var(--fs-sm);
}

.search-results .result-snippet {
  font-size: var(--fs-xs);
  color: var(--text-muted);
  margin-top: 0.15rem;
}

.search-empty {
  text-align: center;
  color: var(--text-muted);
  font-size: var(--fs-sm);
  padding: 1rem;
}

/* Progress bar under header */
.read-progress {
  position: fixed;
  top: var(--header-h);
  left: 0;
  height: 3px;
  width: 0;
  background: var(--blue-light);
  z-index: 99;
  transition: width 0.1s linear;
}

/* ---- Desktop (≥ 1024px) ---- */
@media (min-width: 1024px) {
  .menu-toggle {
    display: none;
  }

  .book-shell {
    grid-template-columns: var(--sidebar-w) minmax(0, 1fr) var(--aside-w);
    max-width: 1400px;
    margin: 0 auto;
  }

  .sidebar {
    position: sticky;
    top: var(--header-h);
    height: calc(100vh - var(--header-h));
    width: var(--sidebar-w);
    transform: none;
    z-index: 1;
    box-shadow: none;
  }

  .sidebar-overlay {
    display: none !important;
  }

  .main-wrap {
    padding: 1.25rem 1.5rem 3rem;
  }

  .aside-panel {
    display: block;
    position: sticky;
    top: calc(var(--header-h) + 1rem);
    height: fit-content;
    max-height: calc(100vh - var(--header-h) - 2rem);
    overflow-y: auto;
    padding: 1rem 0.75rem 1rem 0;
    font-size: var(--fs-sm);
  }

  .aside-sticky-inner {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 0.85rem;
  }

  .aside-sticky-inner h4 {
    margin: 0 0 0.5rem;
    font-size: var(--fs-sm);
    color: var(--navy);
  }

  .cover {
    margin-left: 0;
    margin-right: 0;
    border-radius: var(--radius);
  }

  .era-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .home-toc-era ol {
    columns: 2;
  }

  .back-to-top {
    right: calc(var(--aside-w) + 1.5rem);
  }
}

@media (min-width: 1280px) {
  .era-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

/* Home page: no right aside needed on cover */
.page-home .aside-panel {
  display: none;
}

@media (min-width: 1024px) {
  .page-home .book-shell {
    grid-template-columns: var(--sidebar-w) minmax(0, 1fr);
  }
}

/* ---- Mobile readability (남씨 한국사) ---- */
@media (max-width: 768px) {
  html {
    -webkit-text-size-adjust: 100%;
  }

  .main-content {
    text-align: center;
  }

  .main-content p,
  .main-content .lead,
  .main-content .chapter-desc,
  .main-content .chapter-label,
  .main-content h1,
  .main-content h2,
  .main-content h3,
  .main-content h4,
  .main-content .box-label,
  .cover-inner {
    text-align: center;
    word-break: keep-all;
    overflow-wrap: break-word;
    line-break: strict;
  }

  .main-content p,
  .main-content li,
  .main-content .lead {
    line-height: 1.85;
    letter-spacing: -0.015em;
  }

  .main-content ul,
  .main-content ol {
    display: inline-block;
    text-align: left;
    margin-left: auto;
    margin-right: auto;
    max-width: 36em;
  }

  .main-content .ox-list,
  .main-content .question-list {
    display: block;
    text-align: left;
    max-width: none;
  }

  .main-content .ox-list li,
  .main-content .question-list > li {
    text-align: left;
  }

  .table-scroll,
  .comparison-table,
  .comparison-table th,
  .comparison-table td {
    text-align: left;
  }

  .memory-box,
  .trap-box,
  .tip-box,
  .summary-card {
    text-align: center;
  }

  .memory-box ul,
  .trap-box ul,
  .tip-box ul,
  .summary-card ul {
    display: inline-block;
    text-align: left;
    margin-left: auto;
    margin-right: auto;
  }

  .war-flow {
    text-align: center;
  }

  .timeline {
    text-align: left;
    display: inline-block;
    width: 100%;
    max-width: 36em;
  }

  .chapter-nav .nav-next {
    text-align: center;
  }

  .header-brand {
    text-align: left;
  }

  .chapter-hero,
  .edu-figure {
    text-align: center;
  }

  .chapter-hero figcaption,
  .edu-figure figcaption {
    text-align: center;
    word-break: keep-all;
    overflow-wrap: break-word;
    line-height: 1.55;
    padding-left: 0.85rem;
    padding-right: 0.85rem;
  }

  .king-card .card-body,
  .person-card .card-body,
  .artifact-card h4,
  .artifact-card p {
    word-break: keep-all;
    overflow-wrap: break-word;
  }

  .main-content strong.key-term {
    word-break: keep-all;
  }
}