/**
 * 全站吸顶导航 — 与「关于我们」页 site-header 视觉、交互一致
 * 桌面：滚过原顶栏后从上滑入固定
 * 平板 / 手机：始终吸顶，汉堡展开抽屉
 */
.site-nav {
  --site-nav-primary: #196df4;
  font-family: "SimHei", "Heiti SC", "STHeiti", "Microsoft YaHei", sans-serif;
  display: block;
  position: fixed;
  left: 0;
  top: 0;
  width: 100%;
  z-index: 300;
  background: rgba(255, 255, 255, 0.96);
  backdrop-filter: blur(16px);
  border-bottom: 1px solid rgba(25, 109, 244, 0.1);
  box-shadow: 0 8px 28px rgba(25, 109, 244, 0.1);
  transform: translate3d(0, -110%, 0);
  transition: transform 0.38s cubic-bezier(0.22, 1, 0.36, 1);
  pointer-events: none;
}

.site-nav.is-fixed {
  transform: translate3d(0, 0, 0);
  pointer-events: auto;
}

.site-nav__inner {
  display: flex;
  align-items: center;
  gap: 28px;
  width: min(92%, 1600px);
  height: 72px;
  margin: 0 auto;
}

.site-nav__brand {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-shrink: 0;
  color: inherit;
  text-decoration: none;
}

.site-nav__brand img:first-child {
  width: 48px;
  height: 48px;
  object-fit: contain;
}

.site-nav__brand-text {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.site-nav__brand-en {
  font-size: 15px;
  line-height: 1.2;
  letter-spacing: 0.02em;
  white-space: nowrap;
}

.site-nav__brand-cn {
  width: 78px;
  height: auto;
}

.site-nav__nav {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 36px;
  flex: 1;
  font-size: 16px;
  line-height: 1.4;
}

.site-nav__nav > a {
  padding: 6px 0;
  color: inherit;
  text-decoration: none;
  transition: color 0.2s;
}

.site-nav__nav > a:hover,
.site-nav__nav > a.is-active {
  color: var(--site-nav-primary);
}

.site-nav__dropdown {
  position: relative;
}

.site-nav__dropdown > a {
  display: inline-block;
  padding: 6px 0;
  color: inherit;
  text-decoration: none;
  transition: color 0.2s;
}

.site-nav__dropdown:hover > a,
.site-nav__dropdown:focus-within > a,
.site-nav__dropdown > a.is-active {
  color: var(--site-nav-primary);
}

.site-nav__submenu {
  position: absolute;
  left: 50%;
  top: calc(100% + 10px);
  width: 160px;
  padding: 8px;
  background: #fff;
  border-radius: 12px;
  box-shadow: 0 14px 36px rgba(25, 109, 244, 0.14), 0 2px 8px rgba(15, 40, 90, 0.06);
  border: 1px solid rgba(25, 109, 244, 0.12);
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  transform: translate(-50%, 8px);
  transition: opacity 0.22s ease, transform 0.22s ease, visibility 0.22s ease;
  z-index: 40;
}

.site-nav__submenu::before {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  top: -14px;
  height: 14px;
}

.site-nav__submenu::after {
  content: "";
  position: absolute;
  left: 50%;
  top: -6px;
  width: 12px;
  height: 12px;
  background: #fff;
  border-left: 1px solid rgba(25, 109, 244, 0.12);
  border-top: 1px solid rgba(25, 109, 244, 0.12);
  transform: translateX(-50%) rotate(45deg);
}

.site-nav__dropdown:hover .site-nav__submenu,
.site-nav__dropdown:focus-within .site-nav__submenu {
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
  transform: translate(-50%, 0);
}

.site-nav__submenu a,
.site-nav__submenu [role="menuitem"] {
  display: block;
  padding: 10px 8px;
  font-size: 14px;
  text-align: center;
  color: #3a4454;
  text-decoration: none;
  border-radius: 8px;
  transition: color 0.2s, background-color 0.2s;
}

.site-nav__submenu > * + * { margin-top: 2px; }

.site-nav__submenu a:hover,
.site-nav__submenu a.is-current {
  color: var(--site-nav-primary);
  background: rgba(25, 109, 244, 0.08);
}

.site-nav__submenu [role="menuitem"]:not(a) {
  cursor: default;
}

.site-nav__phone--bar {
  flex-shrink: 0;
  font-size: 16px;
  color: var(--site-nav-primary);
  font-weight: 600;
  white-space: nowrap;
  text-decoration: none;
}

.site-nav__cta--bar {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  height: 40px;
  padding: 0 18px;
  border: none;
  border-radius: 999px;
  background: var(--site-nav-primary);
  color: #fff;
  font-size: 15px;
  font-weight: 600;
  white-space: nowrap;
  text-decoration: none;
  cursor: pointer;
}

.site-nav__toggle,
.site-nav__drawer {
  display: none;
}

@media (prefers-reduced-motion: reduce) {
  .site-nav { transition: none; }
}

@media (max-width: 991px) {
  .site-nav {
    position: sticky;
    top: 0;
    z-index: 300;
    background: rgba(255, 255, 255, 0.96);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid rgba(25, 109, 244, 0.08);
    box-shadow: none;
    transform: none;
    pointer-events: auto;
    transition: none;
  }

  .site-nav__nav,
  .site-nav__phone--bar,
  .site-nav__cta--bar {
    display: none;
  }

  .site-nav__inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    width: 100%;
    max-width: 100%;
    height: 64px;
    padding: 0 16px;
    margin: 0;
  }

  .site-nav__brand img:first-child {
    width: 44px;
    height: 44px;
  }

  .site-nav__brand-en { font-size: 14px; }
  .site-nav__brand-cn { width: 72px; }

  .site-nav__toggle {
    display: flex;
    flex-direction: column;
    justify-content: center;
    gap: 5px;
    width: 40px;
    height: 40px;
    padding: 8px;
    flex-shrink: 0;
    border: none;
    background: none;
    cursor: pointer;
  }

  .site-nav__toggle span {
    display: block;
    width: 100%;
    height: 2px;
    background: #111;
    border-radius: 1px;
    transition: transform 0.2s, opacity 0.2s;
  }

  .site-nav__toggle[aria-expanded="true"] span:nth-child(1) {
    transform: translateY(7px) rotate(45deg);
  }

  .site-nav__toggle[aria-expanded="true"] span:nth-child(2) { opacity: 0; }

  .site-nav__toggle[aria-expanded="true"] span:nth-child(3) {
    transform: translateY(-7px) rotate(-45deg);
  }

  .site-nav__drawer {
    display: flex;
    flex-direction: column;
    gap: 4px;
    padding: 8px 16px 16px;
    background: #fff;
    border-top: 1px solid rgba(0, 0, 0, 0.06);
  }

  .site-nav__drawer[hidden] { display: none; }

  .site-nav__drawer a,
  .site-nav__drawer button,
  .site-nav__drawer .site-nav__sublink {
    display: block;
    padding: 12px 8px;
    font-size: 16px;
    line-height: 1.4;
    text-align: left;
    color: inherit;
    text-decoration: none;
    border: none;
    background: none;
    border-radius: 8px;
    cursor: pointer;
  }

  .site-nav__drawer a:hover,
  .site-nav__drawer a.is-active {
    color: var(--site-nav-primary);
    font-weight: 600;
  }

  .site-nav__sublink {
    margin: 0 4px 0 12px;
    padding: 8px 12px 8px 14px !important;
    font-size: 14px !important;
    color: #556070;
    background: #f4f8fe;
    border-left: 2px solid rgba(25, 109, 244, 0.35);
    border-radius: 0 8px 8px 0;
  }

  span.site-nav__sublink {
    cursor: default;
  }

  a.site-nav__sublink:hover,
  .site-nav__sublink.is-active {
    color: var(--site-nav-primary);
    background: rgba(25, 109, 244, 0.1);
    font-weight: 600;
  }

  .site-nav__phone {
    color: var(--site-nav-primary);
    font-weight: 600;
  }

  .site-nav__cta {
    display: flex;
    align-items: center;
    justify-content: center;
    margin-top: 8px;
    height: 44px;
    border-radius: 999px;
    background: var(--site-nav-primary);
    color: #fff !important;
    text-align: center;
    font-weight: 600;
  }
}