/* ============ 导航栏 SiteNav ============ */
.nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 9000;
  transition: background 0.6s var(--ease-lux), backdrop-filter 0.6s, border-color 0.6s;
  border-bottom: 1px solid transparent;
}
.nav--solid {
  background: rgba(8, 8, 10, 0.82);
  backdrop-filter: blur(18px);
  -webkit-backdrop-filter: blur(18px);
  border-bottom-color: var(--line-soft);
}

.nav-inner {
  width: min(1360px, 94vw);
  margin: 0 auto;
  height: 5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.brand { display: flex; align-items: center; gap: 0.8rem; }
.brand-mark { width: 2.4rem; height: 2.4rem; }
.brand-text { display: flex; flex-direction: column; line-height: 1.15; }
.brand-text strong {
  font-family: var(--serif);
  font-weight: 700;
  font-size: 1.12rem;
  letter-spacing: 0.34em;
}
.brand-text small {
  font-family: var(--latin);
  font-size: 0.6rem;
  letter-spacing: 0.42em;
  color: var(--gold);
}

.nav-links { display: flex; gap: 2.6rem; }
.nav-link {
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.15rem;
  padding: 0.4rem 0;
}
.nav-link-en {
  font-family: var(--latin);
  font-size: 0.58rem;
  letter-spacing: 0.38em;
  color: var(--ink-faint);
  transition: color 0.4s;
}
.nav-link-cn {
  font-size: 0.92rem;
  letter-spacing: 0.22em;
  color: var(--ink);
  transition: color 0.4s;
}
.nav-link::after {
  content: '';
  position: absolute;
  bottom: -2px; left: 50%;
  width: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--gold), transparent);
  transition: width 0.5s var(--ease-lux), left 0.5s var(--ease-lux);
}
.nav-link:hover::after, .nav-link.current::after { width: 100%; left: 0; }
.nav-link:hover .nav-link-cn, .nav-link.current .nav-link-cn { color: var(--gold-hi); }
.nav-link:hover .nav-link-en, .nav-link.current .nav-link-en { color: var(--gold); }

/* ============ 语言切换 LangSwitch ============ */
.lang-switch {
  display: inline-flex;
  align-items: center;
  gap: 0.18rem;
  margin-left: 0.5rem;
  padding: 0.5rem 0.8rem;
  min-height: 2.4rem;
  font-size: 0.74rem;
  letter-spacing: 0.12em;
  color: var(--ink-dim);
  background: transparent;
  border: 1px solid rgba(212, 175, 55, 0.35);
  border-radius: 999px;
  cursor: pointer;
  transition: color 0.35s, border-color 0.35s, background 0.35s;
}
.lang-switch:hover { color: var(--gold-hi); border-color: var(--gold); background: rgba(212,175,55,0.06); }
.lang-switch span { transition: color 0.35s; }
.lang-switch span.on { color: var(--gold-hi); }
.lang-switch-sep { color: var(--ink-faint); }
@media (max-width: 860px) {
  .lang-switch { padding: 0.42rem 0.6rem; margin-left: 0.15rem; }
}

.burger {
  display: none;
  flex-direction: column;
  gap: 6px;
  background: none;
  border: none;
  padding: 8px;
}
.burger span {
  display: block;
  width: 26px; height: 1.5px;
  background: var(--ink);
  transition: transform 0.45s var(--ease-lux), opacity 0.3s;
}
.burger.active span:nth-child(1) { transform: translateY(7.5px) rotate(45deg); }
.burger.active span:nth-child(2) { opacity: 0; }
.burger.active span:nth-child(3) { transform: translateY(-7.5px) rotate(-45deg); }

@media (max-width: 860px) {
  .nav-inner { height: 4.2rem; }
  .brand-mark { width: 2rem; height: 2rem; }
  .brand-text strong { font-size: 1rem; letter-spacing: 0.26em; }
  .brand-text small { font-size: 0.52rem; }
  .burger { display: flex; z-index: 10; }
  .nav-links {
    position: fixed;
    inset: 0;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 2.2rem;
    background: rgba(8, 8, 10, 0.96);
    backdrop-filter: blur(24px);
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.5s var(--ease-lux);
  }
  .nav-links.open { opacity: 1; pointer-events: auto; }
  .nav-links.open .nav-link {
    animation: linkIn 0.7s var(--ease-lux) both;
    animation-delay: calc(var(--i) * 80ms + 0.15s);
  }
  .nav-link-cn { font-size: 1.3rem; }
  @keyframes linkIn {
    from { opacity: 0; transform: translateY(26px); }
    to { opacity: 1; transform: translateY(0); }
  }
}

/* ============ 右侧垂直章节导航 SideRail ============ */
.side-rail {
  position: fixed;
  right: 1.6rem;
  top: 50%;
  transform: translateY(-50%) translateX(12px);
  z-index: 900;
  display: flex;
  flex-direction: column;
  gap: 1.05rem;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.6s var(--ease-lux), transform 0.6s var(--ease-spring-soft);
}
.side-rail.show {
  opacity: 1;
  transform: translateY(-50%) translateX(0);
  pointer-events: auto;
}
.rail-item {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: flex-end;
  background: none;
  border: none;
  padding: 0.15rem 0;
  cursor: pointer;
}
.rail-dot {
  width: 0.42rem;
  height: 0.42rem;
  border-radius: 50%;
  background: rgba(236, 229, 216, 0.28);
  box-shadow: 0 0 0 1px rgba(236, 229, 216, 0.08);
  transition: transform 0.5s var(--ease-spring), background 0.4s, box-shadow 0.4s;
}
.rail-item:hover .rail-dot { background: rgba(245, 227, 172, 0.7); }
.rail-item.active .rail-dot {
  transform: scale(1.75);
  background: var(--gold);
  box-shadow: 0 0 12px rgba(212, 175, 55, 0.55), 0 0 0 1px rgba(245, 227, 172, 0.4);
}
.rail-label {
  position: absolute;
  right: 1.4rem;
  top: 50%;
  transform: translateY(-50%) translateX(8px);
  display: flex;
  align-items: baseline;
  gap: 0.45rem;
  white-space: nowrap;
  font-size: 0.72rem;
  letter-spacing: 0.26em;
  color: var(--gold-hi);
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.4s, transform 0.5s var(--ease-spring-soft);
}
.rail-label i {
  font-family: var(--latin);
  font-style: normal;
  font-size: 0.54rem;
  letter-spacing: 0.2em;
  color: var(--ink-faint);
}
.rail-item:hover .rail-label,
.rail-item.active .rail-label {
  opacity: 1;
  transform: translateY(-50%) translateX(0);
}
.rail-item.active .rail-label i { color: var(--gold); }

@media (max-width: 1100px) {
  .side-rail { display: none; }
}