/* =========================================================
   致远钢结构 · 常见问题栏目页
   同源设计系统：浅蓝 #2C4A7C + 金 #E8943A
   ========================================================= */
:root {
  --blue: #2C4A7C;
  --blue-deep: #1E3A66;
  --blue-footer: #142A4A;
  --blue-overlay: #23426F;
  --border: #5C7BA8;
  --gold: #E8943A;
  --cream: #F4EFE4;
  --ink: #18242F;
  --muted: #5C6B7E;
  --white: #ffffff;
  --radius-card: 12px;
  --radius-btn: 8px;
  --shadow-soft: 0 10px 30px rgba(20, 42, 74, 0.10);
  --shadow-hover: 0 16px 40px rgba(20, 42, 74, 0.18);
  --pad-x: 80px;
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: system-ui, -apple-system, 'Segoe UI', 'Microsoft YaHei', system-ui, sans-serif;
  color: var(--ink);
  background: var(--white);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}
a { text-decoration: none; color: inherit; }
.container { max-width: 1440px; margin: 0 auto; padding: 0 var(--pad-x); }

/* ===================== 顶部导航 ===================== */
.site-header {
  width: 100%;
  position: sticky; top: 0; z-index: 50;
  background: rgba(44, 74, 124, 0.96);
  backdrop-filter: saturate(140%) blur(6px);
  border-bottom: 1px solid rgba(255,255,255,0.12);
}
.nav-inner { display: flex; align-items: center; justify-content: space-between; height: 72px; }
.brand { display: flex; align-items: center; gap: 12px; color: var(--white); font-weight: 700; }
.brand-mark {
  width: 34px; height: 34px; border-radius: 8px;
  background: var(--gold); color: var(--blue-footer);
  display: grid; place-items: center; font-family: system-ui, -apple-system, 'Segoe UI', 'Microsoft YaHei', sans-serif; font-size: 22px; font-weight: 700;
}
.brand-text { font-size: 19px; letter-spacing: .5px; }
.nav-links { display: flex; align-items: center; gap: 30px; }
.nav-links a { color: rgba(255,255,255,0.88); font-size: 15px; transition: color .2s; }
.nav-links a:hover { color: var(--gold); }
.nav-links a.active { color: var(--gold); font-weight: 500; }
.nav-cta {
  background: var(--gold); color: var(--blue-footer) !important;
  padding: 9px 18px; border-radius: var(--radius-btn); font-weight: 500;
}
.nav-cta:hover { background: #F4C888; }
.nav-toggle { display: none; flex-direction: column; gap: 5px; background: none; border: 0; cursor: pointer; padding: 6px; }
.nav-toggle span { width: 24px; height: 2px; background: var(--white); border-radius: 2px; transition: .3s; }

/* ===================== 标题区 ===================== */
.hero-faq {
  background: var(--white);
  padding: 56px 0 48px;
  border-bottom: 1px solid rgba(92,123,168,0.18);
}
.breadcrumb { display: flex; align-items: center; gap: 10px; font-size: 13px; color: #C9D5E5; margin-bottom: 22px; }
.breadcrumb a:hover { color: var(--gold); }
.breadcrumb .current { color: var(--cream); font-weight: 500; }
.kicker { font-family: system-ui, -apple-system, 'Segoe UI', 'Microsoft YaHei', sans-serif; letter-spacing: 3px; color: var(--gold); font-size: 17px; }
.kicker.light { color: var(--gold); }
.hero-title { font-family: system-ui, -apple-system, 'Segoe UI', 'Microsoft YaHei', sans-serif; font-weight: 900; font-size: 46px; color: var(--cream); margin: 6px 0 14px; letter-spacing: 1px; }
.hero-faq .hero-sub { color: #C9D5E5; font-size: 16px; max-width: 720px; }

/* 搜索 */
.faq-search {
  margin-top: 28px; max-width: 640px; position: relative;
  display: flex; align-items: center;
  background: var(--white); border: 1px solid var(--border);
  border-radius: 999px; padding: 4px 16px; box-shadow: var(--shadow-soft);
  transition: border-color .2s, box-shadow .2s;
}
.faq-search:focus-within { border-color: var(--gold); box-shadow: 0 0 0 4px rgba(232,148,58,0.18); }
.search-icon { color: var(--muted); flex: none; }
.faq-search input { flex: 1; border: 0; outline: 0; padding: 14px 12px; font-size: 15px; font-family: inherit; color: var(--ink); background: transparent; }
.search-clear { border: 0; background: none; color: var(--muted); font-size: 22px; cursor: pointer; line-height: 1; padding: 0 4px; display: none; }
.faq-search.has-text .search-clear { display: block; }

/* ===================== 分类筛选 + 列表 ===================== */
.faq-section { padding: 56px 0 80px; background: var(--white); }
.faq-filters { display: flex; flex-wrap: wrap; gap: 12px; margin-bottom: 18px; }
.faq-pill {
  border: 1px solid var(--border); background: var(--white); color: var(--blue-deep);
  padding: 9px 20px; border-radius: 999px; font-size: 14px; cursor: pointer;
  font-family: inherit; transition: all .2s;
}
.faq-pill:hover { border-color: var(--gold); color: var(--gold); }
.faq-pill.active { background: var(--blue); border-color: var(--blue); color: var(--white); }
.faq-count { color: #5C6B7E; font-size: 14px; margin-bottom: 20px; }
.faq-count b { color: var(--blue-footer); }

.faq-list { display: flex; flex-direction: column; gap: 14px; }
.faq-item {
  border: 1px solid rgba(92,123,168,0.28); border-radius: var(--radius-card);
  background: var(--white); overflow: hidden; transition: border-color .2s, box-shadow .2s;
}
.faq-item:hover { border-color: var(--border); box-shadow: var(--shadow-soft); }
.faq-q {
  width: 100%; text-align: left; background: none; border: 0; cursor: pointer;
  display: flex; align-items: center; gap: 16px; padding: 22px 26px; font-family: inherit;
}
.faq-cat-tag {
  flex: none; font-size: 12px; color: var(--gold); border: 1px solid rgba(232,148,58,0.5);
  background: rgba(232,148,58,0.10); padding: 4px 12px; border-radius: 999px; font-weight: 500;
}
.faq-q-text { flex: 1; font-size: 17px; font-weight: 500; color: var(--blue-footer); }
.faq-arrow {
  flex: none; width: 12px; height: 12px; border-right: 2px solid var(--muted); border-bottom: 2px solid var(--muted);
  transform: rotate(45deg); transition: transform .3s; margin-right: 4px;
}
.faq-q[aria-expanded="true"] .faq-arrow { transform: rotate(-135deg); }
.faq-q[aria-expanded="true"] { background: rgba(44,74,124,0.04); }

.faq-a { max-height: 0; overflow: hidden; transition: max-height .35s ease; }
.faq-a-inner { padding: 0 26px 24px 26px; color: #5C6B7E; font-size: 15px; }
.faq-a-inner p { margin-bottom: 10px; }
.faq-a-inner strong { color: var(--blue-deep); }
.faq-a-inner ul { margin: 0 0 10px 20px; }
.faq-a-inner li { margin-bottom: 6px; }

.faq-empty { text-align: center; padding: 50px 20px; color: #5C6B7E; }
.faq-empty p { margin-bottom: 18px; }

/* ===================== CTA ===================== */
.faq-section + .cta { background: var(--blue-overlay); color: var(--white); padding: 60px 0; }
.faq-section + .cta .cta-inner { display: flex; align-items: center; justify-content: space-between; gap: 40px; flex-wrap: wrap; }
.faq-section + .cta .cta-text h2 { font-size: 30px; font-weight: 700; margin: 6px 0 10px; }
.faq-section + .cta .cta-text p { color: rgba(255,255,255,0.82); max-width: 540px; }
.faq-section + .cta .cta-actions { display: flex; gap: 14px; flex-wrap: wrap; }
.btn-primary {
  background: var(--gold); color: var(--blue-footer); padding: 14px 28px;
  border-radius: var(--radius-btn); font-weight: 500; transition: background .2s, transform .2s;
}
.btn-primary:hover { background: #F4C888; transform: translateY(-2px); }
.btn-ghost { border: 1px solid rgba(255,255,255,0.5); color: var(--white); padding: 14px 28px; border-radius: var(--radius-btn); transition: background .2s; }
.btn-ghost:hover { background: rgba(255,255,255,0.12); }

/* ===================== 页脚 ===================== */
.site-footer { width: 100%; background: var(--blue-footer); color: rgba(255,255,255,0.85); padding: 56px 0 26px; }
.footer-inner { display: flex; justify-content: space-between; gap: 50px; flex-wrap: wrap; }
.footer-brand { max-width: 360px; }
.footer-brand p { margin-top: 16px; font-size: 14px; color: rgba(255,255,255,0.7); line-height: 1.8; }
.footer-cols { display: flex; gap: 70px; flex-wrap: wrap; }
.footer-col h4 { color: var(--white); font-size: 15px; margin-bottom: 16px; }
.footer-col a { display: block; font-size: 14px; color: rgba(255,255,255,0.72); margin-bottom: 10px; transition: color .2s; }
.footer-col a:hover { color: var(--gold); }
.footer-bottom {
  width: 100%; max-width: 1440px; margin: 0 auto; margin-top: 40px; padding: 22px 80px 0;
  border-top: 1px solid rgba(255,255,255,0.12);
  display: flex; justify-content: space-between; gap: 16px; flex-wrap: wrap;
  font-size: 13px; color: rgba(255,255,255,0.6);
}

/* ===================== 返回顶部 ===================== */
.back-top {
  position: fixed; right: 26px; bottom: 26px; z-index: 40;
  width: 46px; height: 46px; border-radius: 50%; border: 0; cursor: pointer;
  background: var(--blue); color: var(--white); font-size: 20px;
  box-shadow: var(--shadow-soft); opacity: 0; pointer-events: none; transition: opacity .3s, background .2s;
}
.back-top.show { opacity: 1; pointer-events: auto; }
.back-top:hover { background: var(--blue-deep); }

/* ===================== 响应式 ===================== */
@media (max-width: 1024px) {
  :root { --pad-x: 40px; }
  .hero-title { font-size: 38px; }
  .footer-bottom { padding-left: 32px; padding-right: 32px; }
}
@media (max-width: 768px) {
  :root { --pad-x: 20px; }
  .nav-links {
    position: absolute; top: 72px; left: 0; right: 0;
    flex-direction: column; align-items: flex-start; gap: 0;
    background: var(--blue-deep); padding: 8px 20px 18px;
    max-height: 0; overflow: hidden; transition: max-height .3s;
  }
  .nav-links.open { max-height: 320px; }
  .nav-links a { padding: 12px 0; width: 100%; }
  .nav-toggle { display: flex; }
  .hero-title { font-size: 30px; }
  .faq-section + .cta .cta-inner { flex-direction: column; align-items: flex-start; }
  .faq-q { padding: 18px 18px; gap: 12px; flex-wrap: wrap; }
  .faq-cat-tag { order: -1; }
  .faq-q-text { font-size: 15px; }
  .faq-a-inner { padding: 0 18px 20px; }
  .footer-bottom { flex-direction: column; gap: 8px; padding-left: 24px; padding-right: 24px; }
}