/* ============================================================
   biyich.com 专题页样式 —— 上海seo公司哪家好
   配色与导航/底部沿用官网统一模板（主色 #2196f3）
   ============================================================ */

/* ---------- 基础重置 ---------- */
* { margin: 0; padding: 0; box-sizing: border-box; }
:root {
  --blue: #2196f3;
  --blue-deep: #1976d2;
  --ink: #24242b;
  --gray: #595959;
  --line: #e6e6e6;
  --bg-soft: #f6f9fe;
  --max: 1200px;
}
html { scroll-behavior: smooth; }
body {
  font-family: "SourceHanSansSC", "Microsoft YaHei", "PingFang SC", Arial, sans-serif;
  color: var(--ink);
  background: #fff;
  line-height: 1.7;
  font-size: 15px;
}
a { color: inherit; text-decoration: none; }
img { display: block; max-width: 100%; }
.w { max-width: var(--max); margin: 0 auto; padding: 0 20px; }
.df { display: flex; }
.a-ic { align-items: center; }
.j-sb { justify-content: space-between; }
.j-sc { justify-content: center; }
.f-dc { flex-direction: column; }
.f-wrap, .fl-wrap { flex-wrap: wrap; }
.txt-c { text-align: center; }

/* ============================================================
   顶部导航（对齐 biyich.com 统一模板）
   ============================================================ */
.head {
  position: sticky; top: 0; z-index: 600;
  background: var(--ink);
  box-shadow: 0 2px 8px rgba(0,0,0,.08);
}
.head .headi { height: 72px; }
.logo img { width: 116px; }
.menu ul { list-style: none; display: flex; }
.menu ul li { position: relative; margin-right: 34px; }
.menu ul li:last-child { margin-right: 0; }
.menu ul li a.topa {
  display: flex; align-items: center; height: 72px;
  color: #fff; font-size: 16px;
}
.menu ul li a.topa span { margin-right: 5px; }
.menu ul li a.topa i { font-size: 12px; transition: transform .2s; }
.menu ul li:hover a.topa span,
.menu ul li:hover a.topa i { color: var(--blue); }
.menu ul li:hover a.topa i { transform: rotate(-180deg); }

/* 下拉菜单 */
.submenu {
  position: absolute; top: 72px; left: 50%; transform: translateX(-50%);
  background: #fff; border-radius: 0 0 6px 6px;
  box-shadow: 0 8px 24px rgba(0,0,0,.12); display: none; padding: 22px 26px;
}
.menu ul li:hover .submenu { display: block; }
.submenu .submenu-inner { display: flex; gap: 26px; }
.fuwuitem { width: 150px; }
.fuwuitem h2 { border-bottom: 1px solid var(--line); padding-bottom: 10px; margin-bottom: 10px; }
.fuwuitem h2 a { font-size: 15px; color: var(--ink); font-weight: 600; }
.fuwuitem .li { font-size: 14px; color: var(--gray); padding: 5px 0; }
.fuwuitem .li:hover { color: var(--blue); }
.fangan-list { display: flex; flex-direction: column; gap: 12px; min-width: 200px; }
.fangan-list a { color: var(--gray); font-size: 14px; }
.fangan-list a:hover { color: var(--blue); }

/* 导航右侧咨询按钮 */
.head-cta {
  margin-left: 18px;
}
.head-cta a {
  display: inline-block; background: var(--blue); color: #fff;
  padding: 9px 20px; border-radius: 20px; font-size: 14px;
}
.head-cta a:hover { background: var(--blue-deep); }

/* 移动端菜单开关 */
.nav-toggle { display: none; }

/* ============================================================
   Banner 首屏
   ============================================================ */
.banner {
  background: linear-gradient(135deg, #0e2a47 0%, #123a63 45%, #1976d2 100%);
  color: #fff; padding: 70px 0 80px; position: relative; overflow: hidden;
}
.banner::after {
  content: ""; position: absolute; right: -120px; top: -80px;
  width: 420px; height: 420px; border-radius: 50%;
  background: radial-gradient(circle, rgba(33,150,243,.35), transparent 70%);
}
.banner .crumb { font-size: 13px; opacity: .8; margin-bottom: 18px; }
.banner .crumb a { color: #9ecbff; }
.banner h1 { font-size: 42px; line-height: 1.25; font-weight: 800; margin-bottom: 18px; }
.banner h1 .hl { color: #5ab4ff; }
.banner p.lead { font-size: 18px; opacity: .92; max-width: 760px; margin-bottom: 30px; }
.banner .btns { display: flex; gap: 16px; flex-wrap: wrap; }
.banner .btn {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 13px 30px; border-radius: 26px; font-size: 16px; font-weight: 600;
}
.banner .btn-primary { background: var(--blue); color: #fff; }
.banner .btn-primary:hover { background: #fff; color: var(--blue); }
.banner .btn-ghost { border: 1px solid rgba(255,255,255,.6); color: #fff; }
.banner .btn-ghost:hover { background: #fff; color: #123a63; }
.banner .stat { display: flex; gap: 44px; margin-top: 46px; flex-wrap: wrap; }
.banner .stat .num { font-size: 30px; font-weight: 800; color: #5ab4ff; }
.banner .stat .lab { font-size: 14px; opacity: .85; }

/* ============================================================
   通用区块
   ============================================================ */
section { padding: 64px 0; }
.sec-soft { background: var(--bg-soft); }
.sec-head { text-align: center; max-width: 820px; margin: 0 auto 44px; }
.sec-head .tag {
  display: inline-block; color: var(--blue); font-size: 14px; font-weight: 600;
  letter-spacing: 2px; margin-bottom: 10px;
}
.sec-head h2 { font-size: 30px; font-weight: 800; margin-bottom: 12px; }
.sec-head p { color: var(--gray); font-size: 16px; }

/* 优势卡片 */
.adv-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 22px; }
.adv-card {
  background: #fff; border: 1px solid var(--line); border-radius: 12px;
  padding: 30px 26px; transition: .25s;
}
.adv-card:hover { transform: translateY(-4px); box-shadow: 0 12px 30px rgba(33,150,243,.14); border-color: var(--blue); }
.adv-card .ic {
  width: 54px; height: 54px; border-radius: 12px; background: #eaf4ff;
  display: flex; align-items: center; justify-content: center; margin-bottom: 16px;
}
.adv-card .ic svg { width: 28px; height: 28px; fill: var(--blue); }
.adv-card h3 { font-size: 18px; margin-bottom: 8px; }
.adv-card p { color: var(--gray); font-size: 14px; }

/* 服务能力（网站SEO优化拆解） */
.svc-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; }
.svc-item {
  display: flex; gap: 16px; background: #fff; border: 1px solid var(--line);
  border-radius: 12px; padding: 22px 24px;
}
.svc-item .no {
  flex: 0 0 44px; height: 44px; border-radius: 50%; background: var(--blue);
  color: #fff; font-weight: 700; display: flex; align-items: center; justify-content: center;
}
.svc-item h4 { font-size: 16px; margin-bottom: 4px; }
.svc-item p { color: var(--gray); font-size: 14px; }

/* 选购指南（清单） */
.guide { display: grid; grid-template-columns: 1.1fr .9fr; gap: 40px; align-items: start; }
.guide-list { list-style: none; }
.guide-list li { display: flex; gap: 14px; padding: 16px 0; border-bottom: 1px dashed var(--line); }
.guide-list .ck {
  flex: 0 0 26px; height: 26px; border-radius: 50%; background: #eaf4ff;
  color: var(--blue); display: flex; align-items: center; justify-content: center; font-weight: 700;
}
.guide-list b { color: var(--ink); }
.guide-list span { color: var(--gray); font-size: 14px; }
.guide-card {
  background: #fff; border: 1px solid var(--line); border-radius: 14px; padding: 30px;
}
.guide-card h3 { font-size: 20px; margin-bottom: 14px; }
.guide-card .row { display: flex; justify-content: space-between; padding: 10px 0; border-bottom: 1px solid var(--line); font-size: 14px; }
.guide-card .row span:last-child { color: var(--blue); font-weight: 600; }

/* 服务流程 */
.flow { display: grid; grid-template-columns: repeat(6, 1fr); gap: 12px; }
.flow .step { text-align: center; position: relative; }
.flow .step .dot {
  width: 46px; height: 46px; border-radius: 50%; background: var(--blue); color: #fff;
  display: flex; align-items: center; justify-content: center; font-weight: 700; margin: 0 auto 12px;
}
.flow .step h4 { font-size: 15px; margin-bottom: 4px; }
.flow .step p { font-size: 13px; color: var(--gray); }

/* 行业覆盖 */
.ind-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; }
.ind-item { background: #fff; border: 1px solid var(--line); border-radius: 10px; padding: 20px; text-align: center; }
.ind-item h4 { font-size: 16px; margin-bottom: 6px; }
.ind-item p { font-size: 13px; color: var(--gray); }

/* FAQ */
.faq-list { max-width: 860px; margin: 0 auto; }
.faq-item { border: 1px solid var(--line); border-radius: 10px; margin-bottom: 12px; overflow: hidden; }
.faq-item summary {
  list-style: none; cursor: pointer; padding: 16px 20px; font-weight: 600; font-size: 16px;
  display: flex; justify-content: space-between; align-items: center; background: #fff;
}
.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary::after { content: "+"; color: var(--blue); font-size: 22px; }
.faq-item[open] summary::after { content: "−"; }
.faq-item .ans { padding: 0 20px 18px; color: var(--gray); font-size: 14px; }

/* CTA 咨询块 */
.cta {
  background: linear-gradient(135deg, #123a63, #1976d2);
  color: #fff; border-radius: 16px; padding: 46px 40px;
  display: flex; justify-content: space-between; align-items: center; gap: 24px; flex-wrap: wrap;
}
.cta h3 { font-size: 26px; margin-bottom: 8px; }
.cta p { opacity: .9; }
.cta .phone { font-size: 30px; font-weight: 800; color: #5ab4ff; }
.cta .btn {
  display: inline-block; background: #fff; color: var(--blue); padding: 14px 34px;
  border-radius: 26px; font-weight: 700; font-size: 16px;
}
.cta .btn:hover { background: #eaf4ff; }

/* ============================================================
   底部（对齐 biyich.com 统一模板）
   ============================================================ */
.footer { margin-top: 0; background: #1b1d24; color: #cfd3da; padding: 50px 0 26px; }
.footer .ftcenter { display: flex; gap: 50px; padding-bottom: 36px; border-bottom: 1px solid #34373f; }
.footer .ftserve { flex: 0 0 280px; }
.footer .ftserve .teltit { display: flex; align-items: center; gap: 8px; color: #fff; font-size: 15px; margin-bottom: 8px; }
.footer .ftserve .tel { font-size: 30px; font-weight: 800; color: var(--blue); margin-bottom: 18px; }
.footer .ewm { display: flex; gap: 18px; }
.footer .ewm .itm { text-align: center; }
.footer .ewm .pic { width: 92px; height: 92px; background: #fff; border-radius: 8px; overflow: hidden; }
.footer .ewm .pic img { width: 100%; height: 100%; object-fit: cover; }
.footer .ewm .des { font-size: 12px; margin-top: 6px; color: #b9bdc6; }
.footer .ftmenu { flex: 1; display: flex; gap: 40px; flex-wrap: wrap; }
.footer .ftmenu .ul .lifirst { font-size: 15px; color: #fff; font-weight: 600; margin-bottom: 16px; }
.footer .ftmenu .ul .li { margin-bottom: 10px; }
.footer .ftmenu .ul .li a { color: #b9bdc6; font-size: 14px; }
.footer .ftmenu .ul .li a:hover { color: var(--blue); }
.footer .ftbot { display: flex; justify-content: space-between; align-items: flex-end; padding-top: 26px; gap: 24px; flex-wrap: wrap; }
.footer .botl .pos span { color: #fff; margin-right: 10px; font-size: 14px; }
.footer .botl .dianhua { color: #fff; margin: 10px 0 6px; }
.footer .botl .dizhi p { font-size: 13px; color: #9aa0ab; }
.footer .copy { font-size: 13px; color: #9aa0ab; margin-top: 14px; }
.footer .copy a { color: #9aa0ab; text-decoration: underline; }
.footer .botr { display: flex; gap: 14px; }
.footer .botr a { width: 40px; height: 40px; border-radius: 8px; background: #2a2d36; display: flex; align-items: center; justify-content: center; color: #cfd3da; font-size: 13px; }
.footer .botr a:hover { background: var(--blue); color: #fff; }

/* ============================================================
   响应式
   ============================================================ */
@media (max-width: 980px) {
  .adv-grid { grid-template-columns: repeat(2, 1fr); }
  .svc-grid { grid-template-columns: 1fr; }
  .guide { grid-template-columns: 1fr; }
  .flow { grid-template-columns: repeat(3, 1fr); gap: 18px; }
  .ind-grid { grid-template-columns: repeat(2, 1fr); }
  .footer .ftcenter { flex-direction: column; gap: 30px; }
  .footer .ftserve { flex: none; }
}
@media (max-width: 768px) {
  .head .menu, .head-cta { display: none; }
  .nav-toggle { display: flex; flex-direction: column; gap: 5px; cursor: pointer; padding: 8px; }
  .nav-toggle span { width: 24px; height: 3px; background: #fff; border-radius: 2px; }
  .mobile-nav { display: none; background: #fff; border-top: 1px solid var(--line); }
  .mobile-nav.open { display: block; }
  .mobile-nav a { display: block; padding: 14px 20px; border-bottom: 1px solid var(--line); color: var(--ink); font-size: 15px; }
  .banner h1 { font-size: 30px; }
  .banner .stat { gap: 26px; }
  .adv-grid, .ind-grid { grid-template-columns: 1fr; }
  .flow { grid-template-columns: repeat(2, 1fr); }
  .cta { flex-direction: column; text-align: center; }
}