/* =============================================================
   layout.css — 容器 / 页头 / 页脚 / 区块骨架 / 网格
   ============================================================= */

/* ---------------- 容器 ---------------- */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--gutter);
}
.container--narrow { max-width: var(--container-narrow); }
.container--wide { max-width: 1440px; }

/* ---------------- 区块 ---------------- */
.section {
  position: relative;
  padding-block: clamp(56px, 8vw, var(--sp-10));
}
.section--tight { padding-block: clamp(40px, 5vw, var(--sp-8)); }
.section--soft { background: var(--c-bg-soft); }
.section--mist { background: var(--c-bg-mist); }
.section--cream { background: var(--c-bg-cream); }
.section--dark { background: var(--grad-dark); color: #E8EFFB; }
.section--dark h2,
.section--dark h3,
.section--dark h4 { color: #fff; }

.section-head {
  max-width: 720px;
  margin: 0 auto clamp(32px, 4vw, var(--sp-8));
  text-align: center;
}
.section-head--left { margin-inline: 0; text-align: left; }
.section-head p {
  font-size: var(--fs-lead);
  color: var(--c-ink-500);
}
.section--dark .section-head p { color: #B9C9E6; }

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: var(--sp-2);
  margin-bottom: var(--sp-4);
  font-size: var(--fs-sm);
  font-weight: var(--fw-semibold);
  letter-spacing: var(--ls-wider);
  text-transform: uppercase;
  color: var(--c-teal-600);
}
.eyebrow::before {
  content: "";
  width: 26px;
  height: 2px;
  background: var(--grad-brand);
  border-radius: var(--r-pill);
}
.section--dark .eyebrow { color: var(--c-teal-400); }

/* ---------------- 页头 ---------------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, .88);
  backdrop-filter: saturate(180%) blur(14px);
  -webkit-backdrop-filter: saturate(180%) blur(14px);
  border-bottom: 1px solid transparent;
  transition: border-color var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}
.site-header.is-stuck {
  border-bottom-color: var(--c-line);
  box-shadow: 0 6px 24px rgba(20, 33, 61, .06);
}

.header-inner {
  display: flex;
  align-items: center;
  gap: var(--sp-4);
  min-height: var(--header-h);
  transition: min-height var(--dur) var(--ease);
}
/* 页头容器比正文略宽，为英文长导航留出余量 */
.site-header .container { max-width: var(--container-header); }
.site-header.is-stuck .header-inner { min-height: var(--header-h-sm); }

.brand {
  display: inline-flex;
  align-items: center;
  gap: var(--sp-4);
  flex-shrink: 0;
}
.brand-logo {
  height: 58px;
  width: auto;
  transition: height var(--dur) var(--ease);
}
.site-header.is-stuck .brand-logo { height: 48px; }
.brand-text {
  display: flex;
  flex-direction: column;
  gap: 1px;
  line-height: 1.2;
}
.brand-cn {
  font-size: 15px;
  font-weight: var(--fw-bold);
  color: var(--c-ink-900);
  letter-spacing: .01em;
  white-space: nowrap;
}
.brand-en {
  font-size: 11px;
  font-weight: var(--fw-semibold);
  letter-spacing: var(--ls-wider);
  text-transform: uppercase;
  color: var(--c-teal-600);
  white-space: nowrap;
}
.brand-divider {
  width: 1px;
  height: 32px;
  background: var(--c-line-strong);
}
.brand-mark-gh { height: 34px; width: auto; }

/* 主导航 */
.nav { margin-inline: auto; }
.nav-list {
  display: flex;
  align-items: center;
  gap: clamp(2px, .85vw, 12px);
  margin: 0;
  padding: 0;
  list-style: none;
}
.nav-list li { margin: 0; }
.nav-link {
  position: relative;
  display: block;
  padding: 10px 8px;
  font-size: 15.5px;
  font-weight: var(--fw-medium);
  color: var(--c-ink-700);
  white-space: nowrap;
  border-radius: var(--r-sm);
}
.nav-link::after {
  content: "";
  position: absolute;
  left: 8px; right: 8px;
  bottom: 2px;
  height: 2px;
  background: var(--grad-brand);
  border-radius: var(--r-pill);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--dur) var(--ease);
}
.nav-link:hover { color: var(--c-blue-700); }
.nav-link:hover::after,
.nav-link.is-active::after { transform: scaleX(1); }
.nav-link.is-active { color: var(--c-blue-700); font-weight: var(--fw-semibold); }

/* 右侧动作区 */
.header-actions {
  display: flex;
  align-items: center;
  gap: var(--sp-3);
  flex-shrink: 0;
}

.lang-switch {
  display: inline-flex;
  align-items: center;
  padding: 3px;
  background: var(--c-bg-mist);
  border-radius: var(--r-pill);
}
.lang-switch a {
  padding: 5px 12px;
  font-size: 13px;
  font-weight: var(--fw-semibold);
  color: var(--c-ink-500);
  border-radius: var(--r-pill);
  white-space: nowrap;
}
.lang-switch a:hover { color: var(--c-blue-700); }
.lang-switch a.is-current {
  background: #fff;
  color: var(--c-blue-700);
  box-shadow: var(--sh-1);
}

.social { display: inline-flex; align-items: center; gap: 2px; }
.social a {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 34px; height: 34px;
  color: var(--c-ink-400);
  border-radius: var(--r-pill);
  transition: color var(--dur) var(--ease), background var(--dur) var(--ease);
}
.social a:hover { color: #fff; background: var(--c-blue-600); }
.social svg { width: 17px; height: 17px; }

/* 汉堡按钮 */
.nav-toggle {
  display: none;
  width: 44px; height: 44px;
  padding: 0;
  background: transparent;
  border: 1px solid var(--c-line-strong);
  border-radius: var(--r-sm);
}
.nav-toggle span {
  display: block;
  width: 20px; height: 2px;
  margin: 4px auto;
  background: var(--c-ink-800);
  border-radius: var(--r-pill);
  transition: transform var(--dur) var(--ease), opacity var(--dur) var(--ease);
}
.nav-toggle[aria-expanded="true"] span:nth-child(1) { transform: translateY(6px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
.nav-toggle[aria-expanded="true"] span:nth-child(3) { transform: translateY(-6px) rotate(-45deg); }

.nav-scrim {
  position: fixed;
  inset: 0;
  z-index: 90;
  background: rgba(10, 42, 107, .42);
  opacity: 0;
  visibility: hidden;
  transition: opacity var(--dur) var(--ease), visibility var(--dur);
}
.nav-scrim.is-open { opacity: 1; visibility: visible; }

/* ---------------- 页脚 ---------------- */
.site-footer {
  background: var(--c-ink-900);
  color: #AEBBD1;
  padding-top: clamp(48px, 6vw, var(--sp-9));
}
.site-footer h4 {
  color: #fff;
  font-size: var(--fs-sm);
  font-weight: var(--fw-semibold);
  letter-spacing: var(--ls-wide);
  margin-bottom: var(--sp-5);
}
.footer-grid {
  display: grid;
  grid-template-columns: 1.5fr 1fr 1fr 1fr 1.15fr;
  gap: var(--sp-7) var(--sp-6);
  padding-bottom: var(--sp-8);
}
.footer-brand { display: flex; align-items: center; gap: var(--sp-4); margin-bottom: var(--sp-5); }
.footer-brand img { height: 46px; width: auto; }
.footer-brand .footer-brand-gh { height: 40px; }
.footer-brand .on-dark { background: #fff; border-radius: var(--r-sm); padding: 4px 6px; }
.footer-about p { font-size: var(--fs-sm); line-height: 1.8; color: #93A2BC; }
.footer-links { margin: 0; padding: 0; list-style: none; }
.footer-links li { margin-bottom: 10px; }
.footer-links a { font-size: var(--fs-sm); color: #AEBBD1; }
.footer-links a:hover { color: var(--c-teal-400); }

.footer-contact { margin: 0; padding: 0; list-style: none; font-size: var(--fs-sm); }
.footer-contact li { margin-bottom: 12px; display: flex; gap: 10px; align-items: flex-start; }
.footer-contact svg { width: 16px; height: 16px; margin-top: 4px; flex-shrink: 0; color: var(--c-teal-400); }
.footer-qr { display: flex; gap: var(--sp-4); margin-top: var(--sp-4); }
.footer-qr img {
  width: 92px; height: 92px;
  object-fit: contain;
  background: #fff;
  border-radius: var(--r-sm);
  padding: 5px;
}
.footer-qr figcaption { font-size: var(--fs-xs); color: #93A2BC; margin-top: 6px; text-align: center; }

.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, .1);
  padding-block: var(--sp-5);
  display: flex;
  flex-wrap: wrap;
  gap: var(--sp-3) var(--sp-5);
  align-items: center;
  justify-content: space-between;
  font-size: var(--fs-xs);
  color: #7D8CA6;
}
.footer-bottom a { color: #7D8CA6; }
.footer-bottom a:hover { color: var(--c-teal-400); }

/* ---------------- 通用网格 ---------------- */
.grid { display: grid; gap: var(--sp-5); }
.grid--2 { grid-template-columns: repeat(auto-fit, minmax(320px, 1fr)); }
.grid--3 { grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); }
.grid--4 { grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); }
.grid--auto { grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); }

.split {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: clamp(32px, 5vw, var(--sp-9));
  align-items: center;
}
.split--media-right > .split-media { order: 2; }

/* ---------------- 返回顶部 ---------------- */
.to-top {
  position: fixed;
  right: 20px;
  bottom: 24px;
  z-index: 80;
  width: 46px; height: 46px;
  display: grid;
  place-items: center;
  background: var(--c-blue-600);
  color: #fff;
  border: 0;
  border-radius: var(--r-pill);
  box-shadow: var(--sh-3);
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity var(--dur) var(--ease), transform var(--dur) var(--ease), visibility var(--dur);
}
.to-top.is-visible { opacity: 1; visibility: visible; transform: none; }
.to-top:hover { background: var(--c-blue-700); }
.to-top svg { width: 20px; height: 20px; }

/* ---------------- 响应式 ---------------- */
@media (max-width: 1280px) {
  .social { display: none; }
}
@media (max-width: 1200px) {
  .nav {
    position: fixed;
    inset: 0 0 0 auto;
    width: min(340px, 86vw);
    z-index: 95;
    background: #fff;
    padding: calc(var(--header-h) + 20px) var(--sp-5) var(--sp-6);
    box-shadow: var(--sh-4);
    display: none;
    overflow-y: auto;
    margin: 0;
  }
  .nav.is-open {
    display: block;
    animation: navSlideIn var(--dur) var(--ease) both;
  }
  @keyframes navSlideIn {
    from { transform: translateX(100%); }
    to { transform: none; }
  }
  .nav-list { flex-direction: column; align-items: stretch; gap: 2px; }
  .nav-link {
    padding: 14px 14px;
    font-size: 17px;
    border-bottom: 1px solid var(--c-line);
    border-radius: 0;
  }
  .nav-link::after { display: none; }
  .nav-link.is-active { color: var(--c-blue-700); background: var(--c-blue-050); }
  .nav-toggle { display: block; }
  .brand-divider, .brand-mark-gh { display: none; }
  .brand-logo { height: 46px; }
  .site-header.is-stuck .brand-logo { height: 42px; }
}
@media (max-width: 1360px) {
  .brand-text { display: none; }
}
@media (max-width: 980px) {
  .split { grid-template-columns: 1fr; }
  .split--media-right > .split-media { order: 0; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 560px) {
  .footer-grid { grid-template-columns: 1fr; gap: var(--sp-6); }
  .header-actions .btn { display: none; }
}