/* ============================================================
   layout.css —— 顶栏、三栏、响应式
   ============================================================ */

/* ---------- 顶栏 ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  height: var(--header-h);
  background: rgba(250, 248, 244, 0.85);
  backdrop-filter: saturate(180%) blur(12px);
  -webkit-backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid var(--border);
}
.site-header__inner {
  height: 100%;
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  gap: 16px;
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  color: var(--ink);
  font-size: 0.98rem;
  letter-spacing: 0;
  min-width: 0;
}
.brand:hover { color: var(--ink); }
.brand__mark {
  width: 28px; height: 28px;
  border-radius: 8px;
  background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
  display: block;
  flex: 0 0 auto;
  overflow: hidden;
  box-shadow: var(--shadow-1);
}
.brand__logo {
  width: 100%;
  height: 100%;
  display: block;
  object-fit: cover;
}
.brand__text {
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.site-header__actions {
  display: flex; align-items: center; gap: 8px;
  margin-left: auto;
}
.nav-link {
  font-size: 0.9rem;
  color: var(--ink-soft);
  padding: 6px 10px;
  border-radius: 6px;
}
.nav-link:hover { background: var(--surface-2); color: var(--ink); }

/* 移动端汉堡 */
.nav-toggle {
  display: none;
  background: transparent;
  border: 1px solid var(--border);
  border-radius: 8px;
  width: 36px; height: 36px;
  align-items: center; justify-content: center;
  color: var(--ink-soft);
}
.nav-toggle:hover { background: var(--surface-2); }

/* 顶部阅读进度 */
.read-progress {
  position: absolute;
  bottom: -1px; left: 0;
  height: 2px;
  background: linear-gradient(90deg, var(--primary), var(--accent));
  width: 0%;
  transition: width 0.1s linear;
}

/* ---------- 主体三栏 ---------- */
.layout {
  display: grid;
  grid-template-columns: var(--sidebar-w) minmax(0, 1fr) var(--toc-w);
  max-width: 1400px;
  margin: 0 auto;
  gap: 32px;
  padding: 24px;
  align-items: flex-start;
}

/* 左侧栏 */
.sidebar {
  position: sticky;
  top: calc(var(--header-h) + 24px);
  max-height: calc(100vh - var(--header-h) - 48px);
  overflow-y: auto;
  padding-right: 8px;
  font-size: 0.94rem;
}
.sidebar__title {
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0;
  color: var(--ink-muted);
  margin: 18px 8px 8px;
  font-weight: 700;
}
.sidebar__title--return { margin-top: 24px; }
.sidebar__group { margin-bottom: 12px; }
.sidebar__item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 7px 10px;
  border-radius: 8px;
  color: var(--ink-soft);
  font-size: 0.92rem;
  transition: background .15s var(--ease), color .15s var(--ease);
  line-height: 1.45;
}
.sidebar__item:hover { background: var(--surface-2); color: var(--ink); }
.sidebar__item.is-active {
  background: var(--primary-soft);
  color: var(--primary-deep);
  font-weight: 600;
}
.sidebar__num {
  flex: 0 0 22px;
  font-variant-numeric: tabular-nums;
  color: var(--ink-muted);
  font-size: 0.82rem;
  font-weight: 600;
}
.sidebar__item.is-active .sidebar__num { color: var(--primary); }
.sidebar__dot {
  width: 8px; height: 8px;
  border-radius: 50%;
  border: 1.5px solid var(--border);
  background: transparent;
  margin-left: auto;
  flex: 0 0 8px;
  transition: background .2s var(--ease), border-color .2s var(--ease);
}
.sidebar__item.is-read .sidebar__dot {
  background: var(--success);
  border-color: var(--success);
}

/* 内容主区 */
.content {
  min-width: 0;
  max-width: var(--content-max);
  width: 100%;
  margin: 0 auto;
  padding-bottom: 80px;
}

/* 右侧目录 */
.toc {
  position: sticky;
  top: calc(var(--header-h) + 24px);
  max-height: calc(100vh - var(--header-h) - 48px);
  overflow-y: auto;
  font-size: 0.86rem;
  padding-left: 8px;
  border-left: 1px solid var(--border);
}
.toc__title {
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0;
  color: var(--ink-muted);
  margin: 0 0 10px 12px;
  font-weight: 700;
}
.toc__list { list-style: none; padding: 0; margin: 0; }
.toc__list a {
  display: block;
  padding: 5px 12px;
  color: var(--ink-muted);
  border-left: 2px solid transparent;
  margin-left: -1px;
  line-height: 1.4;
  font-size: 0.85rem;
}
.toc__list a:hover { color: var(--ink-soft); }
.toc__list a.is-active {
  color: var(--primary-deep);
  border-left-color: var(--primary);
  font-weight: 600;
}
.toc__list .toc-h3 { padding-left: 24px; font-size: 0.82rem; }

/* 章末导航 */
.chapter-nav {
  margin-top: 64px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}
.chapter-nav__link {
  display: block;
  padding: 18px 20px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  transition: border-color .2s var(--ease), box-shadow .2s var(--ease), transform .2s var(--ease);
}
.chapter-nav__link:hover {
  border-color: var(--primary);
  box-shadow: var(--shadow-2);
  transform: translateY(-1px);
}
.chapter-nav__dir {
  font-size: 0.78rem;
  color: var(--ink-muted);
  text-transform: uppercase;
  letter-spacing: 0;
  margin-bottom: 4px;
}
.chapter-nav__title {
  font-size: 0.98rem;
  color: var(--ink);
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: 6px;
}
.chapter-nav__link--prev { text-align: left; }
.chapter-nav__link--next { text-align: right; }
.chapter-nav__link--disabled { opacity: 0.4; pointer-events: none; }

/* 底栏 */
.site-footer {
  border-top: 1px solid var(--border);
  background: var(--surface-2);
  padding: 32px 24px;
  color: var(--ink-muted);
  font-size: 0.88rem;
  text-align: center;
  margin-top: 80px;
}
.site-footer a { color: var(--ink-soft); }
.site-footer a:hover { color: var(--primary); }
.site-footer__lead,
.site-footer__note {
  margin: 0;
}
.site-footer__lead {
  margin-bottom: 6px;
}

/* ---------- 响应式 ---------- */
@media (max-width: 1100px) {
  .layout {
    grid-template-columns: var(--sidebar-w) minmax(0, 1fr);
    gap: 24px;
  }
  .toc { display: none; }
}

@media (max-width: 820px) {
  :root {
    --header-h: 52px;
    --sidebar-w: 280px;
  }
  body { font-size: 16px; line-height: 1.8; }
  h1 { font-size: 1.7rem; }
  h2 { font-size: 1.3rem; margin: 2.4rem 0 0.8rem; }
  h3 { font-size: 1.1rem; }

  .layout {
    grid-template-columns: minmax(0, 1fr);
    padding: 16px;
    gap: 0;
  }
  .nav-toggle { display: inline-flex; }
  .nav-link--hide-on-mobile { display: none; }
  .brand__text { max-width: min(58vw, 15em); }

  .sidebar {
    position: fixed;
    top: 0; left: 0; bottom: 0;
    width: 84%;
    max-width: 320px;
    max-height: none;
    background: var(--surface);
    border-right: 1px solid var(--border);
    padding: 16px 12px 32px;
    box-shadow: var(--shadow-3);
    transform: translateX(-100%);
    transition: transform 0.25s var(--ease);
    z-index: 60;
  }
  .sidebar.is-open { transform: translateX(0); }
  .sidebar-scrim {
    position: fixed; inset: 0;
    background: rgba(31, 34, 48, 0.4);
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.2s var(--ease);
    z-index: 55;
  }
  .sidebar-scrim.is-open { opacity: 1; pointer-events: auto; }

  .content { padding-bottom: 60px; }
  .chapter-nav { grid-template-columns: 1fr; }
}