:root {
  --shell-bg: rgba(249, 249, 251, 0.84);
  --shell-surface: #f9f9fb;
  --shell-surface-soft: #f3f3f5;
  --shell-surface-strong: #e8e8ea;
  --shell-border: rgba(194, 198, 209, 0.46);
  --shell-text: #4f5f78;
  --shell-primary: #003363;
  --shell-primary-strong: #104a85;
  --shell-ink: #1a1c1d;
  --shell-max: 92rem;
  /* 与正文 .bp-wrap 共用，保证顶栏 / 页脚 / 主内容左右对齐 */
  --shell-gutter: 2rem;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

a {
  text-decoration: none;
}

.site-header {
  position: fixed;
  inset: 0 0 auto;
  z-index: 70;
  background: var(--shell-bg);
  backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--shell-border);
}

.site-header__inner {
  width: min(calc(100% - var(--shell-gutter)), var(--shell-max));
  margin: 0 auto;
  min-height: 5rem;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.85rem 1.5rem;
  padding-block: 0.95rem;
}

.site-brand {
  flex-shrink: 0;
  color: var(--shell-primary);
  font-family: "Space Grotesk", "Inter", sans-serif;
  font-size: clamp(1rem, 1.2vw + 0.75rem, 1.28rem);
  font-weight: 700;
  letter-spacing: -0.05em;
  line-height: 1;
  text-transform: uppercase;
  white-space: nowrap;
}

.site-nav {
  display: flex;
  align-items: center;
  gap: clamp(1rem, 2vw, 2rem);
  overflow-x: auto;
  scrollbar-width: none;
  /* 与工具栏（语言 + CTA）作为一整块靠右，Logo 独占左侧 */
  margin-left: auto;
}

.site-header__toolbar {
  display: flex;
  align-items: center;
  gap: 0.65rem 1rem;
  flex-shrink: 0;
}

.site-lang {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.35rem 0.5rem;
  border-radius: 0.35rem;
  border: 1px solid rgba(194, 198, 209, 0.55);
  background: rgba(255, 255, 255, 0.55);
}

.site-lang__link {
  font-family: "Inter", sans-serif;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  color: var(--shell-text);
  line-height: 1;
  padding: 0.25rem 0.4rem;
  border-radius: 0.2rem;
  transition:
    color 160ms ease,
    background-color 160ms ease;
}

.site-lang__link:hover,
.site-lang__link:focus-visible {
  color: var(--shell-primary);
}

.site-lang__link.is-active {
  color: #ffffff;
  background: var(--shell-primary-strong);
}

.site-lang__sep {
  color: rgba(115, 119, 129, 0.45);
  font-size: 0.65rem;
  user-select: none;
}

.site-nav::-webkit-scrollbar {
  display: none;
}

.site-nav__link {
  position: relative;
  display: inline-flex;
  align-items: center;
  min-height: 2rem;
  padding: 0.2rem 0;
  color: var(--shell-text);
  font-family: "Inter", sans-serif;
  font-size: 0.92rem;
  font-weight: 600;
  letter-spacing: -0.015em;
  line-height: 1;
  white-space: nowrap;
  transition: color 180ms ease;
}

.site-nav__link::after {
  content: "";
  position: absolute;
  inset: auto 0 -1.45rem;
  height: 2px;
  background: var(--shell-primary-strong);
  transform: scaleX(0);
  transform-origin: center;
  transition: transform 180ms ease;
}

.site-nav__link:hover,
.site-nav__link:focus-visible,
.site-nav__link.is-active {
  color: var(--shell-primary);
}

.site-nav__link:hover::after,
.site-nav__link:focus-visible::after,
.site-nav__link.is-active::after {
  transform: scaleX(1);
}

.site-header__cta {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 8.4rem;
  min-height: 2.85rem;
  padding: 0.75rem 1.35rem;
  border: 1px solid var(--shell-primary);
  background: var(--shell-primary-strong);
  color: #ffffff;
  font-family: "Space Grotesk", "Inter", sans-serif;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.16em;
  line-height: 1;
  text-transform: uppercase;
  transition:
    background-color 180ms ease,
    border-color 180ms ease,
    color 180ms ease,
    transform 180ms ease;
}

.site-header__cta:hover,
.site-header__cta:focus-visible {
  transform: translateY(-1px);
  background: var(--shell-primary);
  border-color: var(--shell-primary);
}

.site-header__cta.is-active {
  background: #ffffff;
  color: var(--shell-primary);
}

.site-footer {
  border-top: 1px solid var(--shell-border);
  background: var(--shell-surface-soft);
}

.site-footer__inner {
  width: min(calc(100% - var(--shell-gutter)), var(--shell-max));
  margin: 0 auto;
  padding: clamp(3.5rem, 7vw, 5rem) 0 clamp(1.5rem, 3vw, 2rem);
}

.site-footer__grid {
  display: grid;
  grid-template-columns: minmax(0, 1.6fr) repeat(3, minmax(0, 1fr));
  gap: clamp(1.5rem, 3vw, 2.5rem);
}

.site-footer__brand {
  display: inline-block;
  color: var(--shell-primary);
  font-family: "Space Grotesk", "Inter", sans-serif;
  font-size: 1.15rem;
  font-weight: 700;
  letter-spacing: -0.04em;
  text-transform: uppercase;
}

.site-footer__intro {
  margin-top: 1rem;
  max-width: 28rem;
  color: var(--shell-text);
  font-size: 0.94rem;
  line-height: 1.8;
}

.site-footer__heading {
  margin-bottom: 1rem;
  color: var(--shell-primary);
  font-family: "Space Grotesk", "Inter", sans-serif;
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.22em;
  text-transform: uppercase;
}

.site-footer__links {
  display: grid;
  gap: 0.75rem;
}

.site-footer__links a,
.site-footer__links p {
  color: var(--shell-text);
  font-size: 0.84rem;
  line-height: 1.7;
  transition: color 180ms ease;
}

.site-footer__links a:hover,
.site-footer__links a:focus-visible {
  color: var(--shell-primary);
}

.site-footer__bottom {
  margin-top: 2rem;
  padding-top: 1rem;
  border-top: 1px solid rgba(194, 198, 209, 0.32);
  color: #737781;
  font-family: "Space Grotesk", "Inter", sans-serif;
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
}

@media (max-width: 767px) {
  :root {
    --shell-gutter: 1.5rem;
  }

  .site-header__inner {
    width: min(calc(100% - var(--shell-gutter)), var(--shell-max));
    gap: 0.8rem 1rem;
    padding-block: 0.85rem;
  }

  .site-brand {
    font-size: 0.96rem;
  }

  .site-header__toolbar {
    /* 首行仅 Logo + 工具栏时，把语言/CTA 顶到右侧 */
    margin-left: auto;
    flex-wrap: wrap;
    justify-content: flex-end;
  }

  .site-header__cta {
    min-width: auto;
    padding-inline: 1rem;
    font-size: 0.68rem;
    letter-spacing: 0.14em;
  }

  .site-nav {
    order: 3;
    width: 100%;
    margin-left: 0;
    margin-right: 0;
    padding-top: 0.85rem;
    border-top: 1px solid rgba(194, 198, 209, 0.34);
    gap: 1rem;
  }

  .site-nav__link::after {
    bottom: -0.85rem;
  }

  .site-footer__grid {
    grid-template-columns: 1fr;
    gap: 1.75rem;
  }
}