/* ============================================================
   QQ知识百科 · 全站样式
   移动优先：375px 起，640 / 960 / 1200 逐级增强
   ============================================================ */

:root{
  --ink:#0E1B2C;
  --ink-2:#2B3A55;
  --muted:#5B6B84;
  --brand:#1E6FFF;
  --brand-2:#22D3EE;
  --brand-soft:#EAF2FF;
  --accent:#F59E0B;
  --ok:#10B981;
  --bg:#F4F7FB;
  --card:#FFFFFF;
  --line:#E2E8F0;
  --radius:18px;
  --radius-sm:12px;
  --shadow:0 10px 30px rgba(14,27,44,.08);
  --font:"PingFang SC","Microsoft YaHei","Segoe UI",system-ui,-apple-system,sans-serif;
}

*,*::before,*::after{box-sizing:border-box}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
body{
  margin:0;
  font-family:var(--font);
  color:var(--ink);
  background:var(--bg);
  line-height:1.75;
  font-size:16px;
}
img{max-width:100%;display:block}
a{color:var(--brand);text-decoration:none}
a:hover{text-decoration:none}
h1,h2,h3,h4{line-height:1.3;margin:0 0 .4em;font-weight:700}
p{margin:0 0 1em}
ul{margin:0 0 1em;padding-left:1.3em}
button{font-family:inherit}

.container{width:100%;max-width:1160px;margin:0 auto;padding:0 20px}

/* ---------- 无障碍 ---------- */
.skip-link{
  position:absolute;left:-999px;top:0;z-index:200;
  background:var(--ink);color:#fff;padding:10px 16px;border-radius:0 0 10px 0;
}
.skip-link:focus{left:0}
:focus-visible{outline:3px solid var(--brand-2);outline-offset:2px;border-radius:4px}

/* ---------- 顶部导航 ---------- */
.site-header{
  position:sticky;top:0;z-index:60;
  background:rgba(255,255,255,.88);
  -webkit-backdrop-filter:blur(12px);backdrop-filter:blur(12px);
  border-bottom:1px solid var(--line);
  transition:box-shadow .3s;
}
.site-header.scrolled{box-shadow:0 6px 24px rgba(14,27,44,.08)}
.nav-wrap{display:flex;align-items:center;justify-content:space-between;height:64px;gap:16px}
.brand{display:flex;align-items:center;gap:10px;color:var(--ink)}
.brand img{width:38px;height:38px;border-radius:10px}
.brand-name{font-size:19px;font-weight:800;letter-spacing:.5px}
.nav{display:none}
.nav.open{
  display:flex;flex-direction:column;gap:2px;
  position:absolute;top:64px;left:0;right:0;z-index:59;
  background:#fff;border-bottom:1px solid var(--line);
  padding:10px 20px 16px;
}
.nav-link{
  color:var(--ink-2);font-weight:600;padding:11px 6px;
  border-bottom:1px solid transparent;
}
.nav-link.active{color:var(--brand)}
.nav-link:hover{color:var(--brand)}
.nav-toggle{
  width:44px;height:44px;border:1px solid var(--line);border-radius:10px;
  background:#fff;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:5px;
  cursor:pointer;
}
.nav-toggle span{display:block;width:20px;height:2px;background:var(--ink);border-radius:2px;transition:transform .25s,opacity .25s}
.nav-toggle[aria-expanded="true"] span:nth-child(1){transform:translateY(7px) rotate(45deg)}
.nav-toggle[aria-expanded="true"] span:nth-child(2){opacity:0}
.nav-toggle[aria-expanded="true"] span:nth-child(3){transform:translateY(-7px) rotate(-45deg)}

/* ---------- 按钮 ---------- */
.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:8px;
  padding:13px 26px;border-radius:999px;font-weight:700;font-size:15px;
  cursor:pointer;border:1px solid transparent;transition:transform .2s,box-shadow .2s,background .2s;
  min-height:44px;
}
.btn svg{flex:none}
.btn-primary{
  background:linear-gradient(120deg,var(--brand),var(--brand-2));color:#fff;
  box-shadow:0 8px 20px rgba(30,111,255,.32);
}
.btn-primary:hover{transform:translateY(-2px);box-shadow:0 12px 26px rgba(30,111,255,.4)}
.btn-ghost{background:rgba(255,255,255,.12);color:#fff;border-color:rgba(255,255,255,.55)}
.btn-ghost:hover{background:rgba(255,255,255,.22)}
.btn-line{background:#fff;color:var(--brand);border-color:var(--brand)}
.btn-line:hover{background:var(--brand-soft)}

/* ---------- Hero（首页） ---------- */
.hero{
  background:url("../pic/hero-bg.png") center/cover no-repeat;
  color:#fff;padding:70px 0 84px;
}
.hero-inner{max-width:660px}
.eyebrow{
  display:inline-flex;align-items:center;gap:8px;
  background:rgba(255,255,255,.14);border:1px solid rgba(255,255,255,.28);
  color:#fff;font-size:13px;font-weight:700;letter-spacing:1px;
  padding:6px 14px;border-radius:999px;margin-bottom:18px;
}
.hero h1{font-size:34px;line-height:1.22;margin-bottom:16px}
.hero .lead{font-size:16px;color:rgba(255,255,255,.88);max-width:34em;margin-bottom:26px}
.hero-cta{display:flex;flex-wrap:wrap;gap:12px;margin-bottom:22px}
.hero-note{font-size:13px;color:rgba(255,255,255,.66)}

/* ---------- 数据条 ---------- */
.stats{border-bottom:1px solid var(--line)}
.stats-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:12px;padding:22px 0}
.stat{
  background:rgba(255,255,255,.75);border:1px solid var(--line);border-radius:var(--radius-sm);
  padding:16px 14px;text-align:center;
}
.stat b{display:block;font-size:26px;color:var(--brand);line-height:1.2}
.stat span{font-size:13px;color:var(--muted)}

/* ---------- 通用区块 ---------- */
.sec{padding:56px 0}
.sec-head{margin-bottom:30px;max-width:760px}
.sec-head .eyebrow{
  background:var(--brand-soft);border-color:#CFE0FF;color:var(--brand);
}
.sec-head h2{font-size:27px;margin-bottom:10px}
.sec-head .lead{color:var(--muted);font-size:15px}
.center{text-align:center;margin-left:auto;margin-right:auto}

/* ---------- 卡片网格 ---------- */
.grid{display:grid;gap:18px}
.grid-3{grid-template-columns:1fr}
.grid-6{grid-template-columns:repeat(2,1fr);gap:16px}
.card{
  background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  overflow:hidden;box-shadow:var(--shadow);display:flex;flex-direction:column;
  transition:transform .25s,box-shadow .25s;
}
.card:hover{transform:translateY(-4px);box-shadow:0 16px 34px rgba(14,27,44,.13)}
.card img{width:100%;height:auto;aspect-ratio:16/10;object-fit:cover}
.card-body{padding:18px 20px 22px;display:flex;flex-direction:column;gap:8px;flex:1}
.card-body h3{font-size:19px;margin:0}
.card-body p{color:var(--muted);font-size:14px;margin:0;flex:1}
.card-link{
  display:inline-flex;align-items:center;gap:6px;font-weight:700;font-size:14px;color:var(--brand);
}
.card-link svg{transition:transform .2s}
.card:hover .card-link svg{transform:translateX(4px)}
.card-meta{font-size:12px;color:var(--muted);display:flex;gap:8px;align-items:center}

/* ---------- 双栏 ---------- */
.split{display:grid;grid-template-columns:1fr;gap:30px;align-items:start}
.level-icons{display:flex;gap:14px;margin:18px 0 6px}
.level-icon{width:64px;height:64px}
.formula{
  background:var(--ink);color:#fff;border-radius:var(--radius-sm);
  padding:14px 18px;font-weight:700;letter-spacing:.5px;
  display:inline-block;margin:10px 0 4px;
}

/* ---------- 表格 ---------- */
.tbl-wrap{overflow-x:auto;border:1px solid var(--line);border-radius:var(--radius-sm);background:#fff}
table{width:100%;border-collapse:collapse;min-width:560px;font-size:14px}
caption{caption-side:bottom;font-size:12px;color:var(--muted);padding:10px 4px 4px;text-align:left}
th,td{padding:13px 14px;text-align:left;border-bottom:1px solid var(--line);vertical-align:top}
th{background:var(--brand-soft);color:var(--ink);font-weight:700;white-space:nowrap}
tbody tr:last-child td{border-bottom:none}
td.center-t{text-align:center}
tr:nth-child(even) td{background:#FAFCFF}

/* ---------- 时间轴 ---------- */
.tl{position:relative;padding-left:30px;margin-top:6px}
.tl::before{
  content:"";position:absolute;left:10px;top:8px;bottom:8px;width:2px;
  background:linear-gradient(180deg,var(--brand),var(--brand-2));
}
.tl-item{position:relative;padding:0 0 30px}
.tl-item:last-child{padding-bottom:0}
.tl-item::before{
  content:"";position:absolute;left:-26px;top:7px;width:14px;height:14px;border-radius:50%;
  background:#fff;border:3px solid var(--brand);
}
.tl-time{font-weight:800;color:var(--brand);font-size:14px;letter-spacing:.5px}
.tl-item h3{font-size:19px;margin:2px 0 4px}
.tl-item p{color:var(--muted);font-size:14px;margin:0}

/* ---------- 号段详解 ---------- */
.seg{
  display:grid;grid-template-columns:1fr;gap:20px;align-items:center;
  background:#fff;border:1px solid var(--line);border-radius:var(--radius);
  padding:18px;margin-bottom:22px;box-shadow:var(--shadow);
}
.seg img{border-radius:var(--radius-sm);aspect-ratio:16/10;object-fit:cover;width:100%}
.seg h3{font-size:21px;margin-bottom:8px}
.seg h3 .tag{
  display:inline-block;vertical-align:middle;margin-left:8px;
  background:var(--brand-soft);color:var(--brand);font-size:12px;font-weight:700;
  padding:3px 10px;border-radius:999px;
}
.seg p{color:var(--ink-2);font-size:15px;margin-bottom:10px}
.seg ul{margin-bottom:4px}
.seg li{font-size:14px;color:var(--muted);margin-bottom:4px}

/* ---------- 文章页 ---------- */
.banner{
  background:url("../pic/banner-common.png") center/cover no-repeat;
  color:#fff;padding:54px 0 58px;
}
.banner h1{font-size:30px;margin-bottom:8px}
.banner p{color:rgba(255,255,255,.85);margin:0;max-width:36em}
.crumbs{display:flex;flex-wrap:wrap;gap:6px;align-items:center;font-size:13px;color:rgba(255,255,255,.7);margin-bottom:14px}
.crumbs a{color:rgba(255,255,255,.85)}
.crumbs a:hover{color:#fff}
.crumbs .sep{opacity:.5}

.chips{display:flex;flex-wrap:wrap;gap:10px;margin-bottom:30px}
.chip{
  border:1px solid var(--line);background:#fff;color:var(--ink-2);
  padding:8px 18px;border-radius:999px;font-size:14px;font-weight:600;cursor:pointer;
  transition:all .2s;min-height:40px;
}
.chip:hover{border-color:var(--brand);color:var(--brand)}
.chip.on{background:linear-gradient(120deg,var(--brand),var(--brand-2));color:#fff;border-color:transparent}

.article{
  background:#fff;border:1px solid var(--line);border-radius:var(--radius);
  box-shadow:var(--shadow);margin-bottom:30px;overflow:hidden;
  display:grid;grid-template-columns:1fr;
}
.article .media img{width:100%;height:100%;aspect-ratio:16/9;object-fit:cover}
.article-body{padding:24px 22px 26px}
.article-body h2{font-size:22px;margin-bottom:8px}
.article-body h3{font-size:17px;margin:18px 0 8px;color:var(--ink-2)}
.article-body p,.article-body li{font-size:15px;color:var(--ink-2)}
.src-line{font-size:13px;color:var(--muted);border-top:1px dashed var(--line);margin-top:16px;padding-top:12px}

/* ---------- FAQ ---------- */
.faq{background:#fff;border:1px solid var(--line);border-radius:var(--radius);box-shadow:var(--shadow)}
.faq-item{border-bottom:1px solid var(--line)}
.faq-item:last-child{border-bottom:none}
.faq-q{
  width:100%;display:flex;justify-content:space-between;align-items:center;gap:14px;
  background:none;border:none;cursor:pointer;text-align:left;
  padding:18px 20px;font-size:16px;font-weight:700;color:var(--ink);min-height:56px;
}
.faq-q svg{flex:none;transition:transform .25s}
.faq-item.open .faq-q svg{transform:rotate(180deg)}
.faq-a{display:grid;grid-template-rows:0fr;transition:grid-template-rows .3s ease}
.faq-item.open .faq-a{grid-template-rows:1fr}
.faq-a-in{overflow:hidden}
.faq-a-in p{margin:0;padding:0 20px 20px;color:var(--muted);font-size:15px}

/* ---------- 联系我们 ---------- */
.contact-grid{display:grid;grid-template-columns:1fr;gap:18px;margin-bottom:34px}
.contact-card{
  background:#fff;border:1px solid var(--line);border-radius:var(--radius);
  padding:24px 22px;box-shadow:var(--shadow);display:flex;gap:16px;align-items:flex-start;
}
.contact-card .ico{
  flex:none;width:52px;height:52px;border-radius:14px;
  background:linear-gradient(135deg,var(--brand),var(--brand-2));
  display:flex;align-items:center;justify-content:center;color:#fff;
}
.contact-card h3{font-size:17px;margin-bottom:4px}
.contact-card p{margin:0;font-size:14px;color:var(--muted)}
.contact-card .mail{color:var(--brand);font-weight:700}

.form-card{
  background:#fff;border:1px solid var(--line);border-radius:var(--radius);
  box-shadow:var(--shadow);padding:26px 22px;
}
.form-card h2{font-size:22px;margin-bottom:6px}
.form-card .hint{font-size:14px;color:var(--muted);margin-bottom:22px}
.field{margin-bottom:18px}
.field label{display:block;font-weight:700;font-size:14px;margin-bottom:8px}
.field input,.field textarea,.field select{
  width:100%;padding:12px 14px;font-size:16px;font-family:inherit;
  border:1px solid var(--line);border-radius:10px;background:#FAFCFF;color:var(--ink);
  transition:border-color .2s,box-shadow .2s;
}
.field input:focus,.field textarea:focus,.field select:focus{
  outline:none;border-color:var(--brand);box-shadow:0 0 0 3px rgba(30,111,255,.15);
}
.field textarea{min-height:140px;resize:vertical}
.field .err{color:#DC2626;font-size:13px;margin-top:6px;display:none}
.field.bad input,.field.bad textarea{border-color:#DC2626}
.field.bad .err{display:block}
.form-ok{
  display:none;background:#ECFDF5;border:1px solid #A7F3D0;color:#047857;
  border-radius:12px;padding:14px 16px;font-size:14px;margin-top:16px;
}
.form-ok.show{display:block}

.note-box{
  background:#FFFBEB;border:1px solid #FDE68A;border-radius:var(--radius);
  padding:20px 22px;margin:34px 0 0;
}
.note-box h3{font-size:17px;margin-bottom:8px;color:#92400E}
.note-box p{font-size:14px;color:#78350F;margin-bottom:8px}
.note-box p:last-child{margin-bottom:0}

/* ---------- CTA ---------- */
.cta{
  background:linear-gradient(120deg,var(--ink),#14355F);color:#fff;
  border-radius:24px;padding:44px 26px;text-align:center;margin:10px 0 0;
}
.cta h2{font-size:24px;margin-bottom:10px}
.cta p{color:rgba(255,255,255,.82);max-width:34em;margin:0 auto 22px}
.cta .hero-cta{justify-content:center}

/* ---------- 页脚 ---------- */
.site-footer{background:var(--ink);color:#C6D2E3;margin-top:70px;font-size:14px}
.footer-grid{display:grid;grid-template-columns:1fr;gap:28px;padding:46px 0 30px}
.footer-col h3{color:#fff;font-size:16px;margin-bottom:14px}
.footer-brand{display:flex;align-items:center;gap:10px;color:#fff;font-weight:800;font-size:18px;margin-bottom:12px}
.footer-brand img{width:34px;height:34px;border-radius:9px}
.footer-col p{margin:0;color:#9FB0C6}
.footer-col a{display:block;color:#C6D2E3;padding:4px 0}
.footer-col a:hover{color:#fff}
.footer-bottom{border-top:1px solid rgba(255,255,255,.1);padding:18px 0 22px;color:#8FA1B9;font-size:13px}
.footer-bottom p{margin:4px 0}

/* ---------- 返回顶部 / Toast ---------- */
.to-top{
  position:fixed;right:18px;bottom:18px;z-index:70;
  width:46px;height:46px;border-radius:50%;border:none;cursor:pointer;
  background:linear-gradient(135deg,var(--brand),var(--brand-2));color:#fff;
  display:flex;align-items:center;justify-content:center;
  box-shadow:0 10px 24px rgba(30,111,255,.4);
  opacity:0;visibility:hidden;transform:translateY(10px);transition:all .25s;
}
.to-top.show{opacity:1;visibility:visible;transform:none}
.toast{
  position:fixed;left:50%;bottom:26px;transform:translateX(-50%) translateY(16px);z-index:90;
  background:var(--ink);color:#fff;padding:13px 20px;border-radius:12px;font-size:14px;
  box-shadow:0 14px 30px rgba(0,0,0,.25);
  opacity:0;visibility:hidden;transition:all .3s;max-width:calc(100vw - 40px);
}
.toast.show{opacity:1;visibility:visible;transform:translateX(-50%) translateY(0)}

/* ---------- 滚动揭示 ---------- */
.rv{opacity:0;transform:translateY(16px);transition:opacity .6s ease,transform .6s ease}
.rv.in{opacity:1;transform:none}

/* ---------- 断点增强 ---------- */
@media (min-width:640px){
  .stats-grid{grid-template-columns:repeat(4,1fr)}
  .grid-3{grid-template-columns:repeat(2,1fr)}
  .grid-6{grid-template-columns:repeat(3,1fr)}
  .split{grid-template-columns:1fr 1fr;gap:40px}
  .seg{grid-template-columns:300px 1fr;padding:22px}
  .article{grid-template-columns:320px 1fr}
  .contact-grid{grid-template-columns:repeat(2,1fr)}
  .footer-grid{grid-template-columns:repeat(2,1fr)}
  .hero{padding:96px 0 110px}
  .hero h1{font-size:46px}
  .sec{padding:70px 0}
}
@media (min-width:960px){
  .grid-3{grid-template-columns:repeat(3,1fr)}
  .footer-grid{grid-template-columns:1.4fr 1fr 1fr 1.2fr;gap:40px}
  .nav{display:flex;align-items:center;gap:6px}
  .nav-link{padding:9px 14px;font-size:15px}
  .nav-toggle{display:none}
  .sec-head h2{font-size:32px}
  .banner h1{font-size:36px}
}
@media (min-width:1200px){
  .container{padding:0 24px}
  .hero h1{font-size:54px}
  .hero .lead{font-size:17px}
}

/* ---------- 减少动效 ---------- */
@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{transition:none!important;animation:none!important}
  .rv{opacity:1;transform:none}
}