/* 比特浏览器 仿官网设计系统（采样自 https://www.bitbrowser.cn）
   主色 #3370ff · 文字 #565f74 · 标题 #2a3142 · 紫辅 #5756ff · 字体 Inter/PingFang */
*{box-sizing:border-box;margin:0;padding:0}
:root{
  --brand:#3370ff; --brand-d:#2865e9; --brand2:#5756ff;
  --ink:#2a3142; --body:#3d4663; --muted:#565f74; --line:#e6e8ee; --line2:#cbd3e6;
  --bg:#fff; --bg-soft:#f4f7ff; --bg-soft2:#eef2fb;
  --teal:#209e91; --orange:#fb9247; --red:#ff6060; --cyan:#00b8eb;
  --radius:14px; --shadow:0 10px 30px rgba(51,112,255,.08); --shadow-s:0 4px 16px rgba(20,30,60,.06);
  --maxw:1180px;
}
html{scroll-behavior:smooth}
body{font-family:Inter,"PingFang SC","Microsoft YaHei",Roboto,-apple-system,"Helvetica Neue",Arial,sans-serif;
  color:var(--body);background:var(--bg);line-height:1.7;-webkit-font-smoothing:antialiased}
.wrap{max-width:var(--maxw);margin:0 auto;padding:0 24px}
a{color:var(--brand);text-decoration:none}
a:hover{text-decoration:underline}
img{max-width:100%;height:auto;display:block}
h1,h2,h3,h4{line-height:1.25;color:var(--ink);font-weight:700}
p{margin:0 0 1em}
section{position:relative}

/* ---------- 按钮 ---------- */
.btn{display:inline-flex;align-items:center;gap:8px;padding:11px 24px;border-radius:10px;
  background:var(--brand);color:#fff;font-weight:600;font-size:15px;border:1px solid var(--brand);
  transition:.18s;box-shadow:0 6px 16px rgba(51,112,255,.25)}
.btn:hover{background:var(--brand-d);text-decoration:none;transform:translateY(-1px)}
.btn.ghost{background:#fff;color:var(--brand);box-shadow:none;border:1px solid var(--line2)}
.btn.ghost:hover{background:var(--bg-soft);border-color:var(--brand)}
.btn.lg{padding:14px 32px;font-size:16px}

/* ---------- 顶栏 ---------- */
.site-hd{position:sticky;top:0;z-index:50;background:rgba(255,255,255,.92);
  backdrop-filter:saturate(180%) blur(10px);border-bottom:1px solid var(--line)}
.site-hd .bar{display:flex;align-items:center;gap:28px;height:66px}
.brand{display:flex;align-items:center}
.brand img{height:30px;width:auto}
.nav{display:flex;gap:22px;flex:1;flex-wrap:wrap}
.nav a{color:var(--muted);font-size:15px;font-weight:500}
.nav a:hover{color:var(--brand);text-decoration:none}
.site-hd .btn{margin-left:auto}

/* ---------- Hero ---------- */
.hero{background:radial-gradient(1200px 480px at 80% -10%,#e9efff 0,rgba(244,247,255,0) 60%),linear-gradient(180deg,#f5f8ff 0,#fff 70%);
  padding:64px 0 40px;overflow:hidden}
.hero .wrap{display:grid;grid-template-columns:1.05fr .95fr;gap:40px;align-items:center}
.hero h1{font-size:46px;letter-spacing:-.5px;margin:0 0 6px}
.hero .sub{font-size:30px;font-weight:700;color:var(--brand);margin:0 0 18px}
.hero .lead{font-size:18px;color:var(--muted);margin:0 0 26px;max-width:540px}
.hero .cta{display:flex;gap:14px;flex-wrap:wrap}
.hero .meta{margin-top:18px;color:var(--muted);font-size:14px;display:flex;gap:18px;flex-wrap:wrap}
.hero-art{position:relative;min-height:420px}

/* 功能放射图（hero 彩色卡片·复刻官网）*/
.node-canvas{position:relative;width:100%;height:430px}
.node-canvas .core{position:absolute;left:50%;top:50%;transform:translate(-50%,-50%);
  width:104px;height:104px;border-radius:26px;background:linear-gradient(135deg,#3370ff,#5756ff);
  display:flex;align-items:center;justify-content:center;box-shadow:0 16px 40px rgba(51,112,255,.4);z-index:3}
.node-canvas .core svg{width:54px;height:54px}
.chip{position:absolute;z-index:2;display:inline-flex;align-items:center;gap:7px;padding:9px 15px;border-radius:12px;
  color:#fff;font-weight:600;font-size:14px;box-shadow:0 12px 26px rgba(20,30,60,.18);white-space:nowrap}
.chip i{width:8px;height:8px;border-radius:50%;background:rgba(255,255,255,.85)}
.chip.c1{background:#3370ff;left:2%;top:8%}
.chip.c2{background:#5756ff;right:0;top:2%}
.chip.c3{background:#209e91;right:-2%;top:38%}
.chip.c4{background:#fb9247;right:4%;bottom:10%}
.chip.c5{background:#ff6060;left:6%;bottom:4%}
.chip.c6{background:#00b8eb;left:-2%;top:44%}
.node-canvas .lines{position:absolute;inset:0;z-index:1}
.spark{position:absolute;opacity:.9}

/* ---------- 通用 section ---------- */
.band{padding:64px 0}
.band.soft{background:var(--bg-soft)}
.sec-head{text-align:center;max-width:720px;margin:0 auto 40px}
.sec-head h2{font-size:34px;margin:0 0 12px}
.sec-head p{font-size:17px;color:var(--muted);margin:0}
.eyebrow{display:inline-block;color:var(--brand);font-weight:700;font-size:14px;letter-spacing:.5px;
  background:var(--bg-soft);padding:5px 14px;border-radius:999px;margin-bottom:14px}

/* 功能卡格 */
.grid{display:grid;gap:22px}
.grid.g3{grid-template-columns:repeat(3,1fr)}
.grid.g2{grid-template-columns:repeat(2,1fr)}
.card{background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:26px;transition:.2s}
.card:hover{box-shadow:var(--shadow);transform:translateY(-3px);border-color:#dbe3f7}
.card .ico{width:60px;height:60px;margin-bottom:14px}
.card h3{font-size:19px;margin:0 0 8px}
.card p{color:var(--muted);font-size:15px;margin:0}

/* 信任徽章 */
.trust{display:flex;gap:34px;justify-content:center;align-items:center;flex-wrap:wrap;opacity:.92}
.trust img{height:34px;width:auto}
.stars{color:var(--orange);font-weight:700;letter-spacing:2px}

/* 数据条 */
.stats{display:grid;grid-template-columns:repeat(4,1fr);gap:20px;text-align:center}
.stats .n{font-size:38px;font-weight:800;color:var(--brand);line-height:1}
.stats .l{color:var(--muted);font-size:15px;margin-top:8px}

/* ---------- 价格卡 ---------- */
.price-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:20px;align-items:stretch}
.plan{background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:28px 24px;display:flex;flex-direction:column}
.plan.feature{border:2px solid var(--brand);box-shadow:var(--shadow);position:relative}
.plan.feature .tag{position:absolute;top:-12px;left:50%;transform:translateX(-50%);background:var(--brand);color:#fff;
  font-size:12px;font-weight:700;padding:4px 14px;border-radius:999px}
.plan h3{font-size:20px;margin:0 0 6px}
.plan .pr{font-size:34px;font-weight:800;color:var(--ink);margin:8px 0}
.plan .pr small{font-size:15px;color:var(--muted);font-weight:500}
.plan ul{list-style:none;margin:14px 0 22px;padding:0}
.plan li{padding:7px 0 7px 26px;position:relative;color:var(--body);font-size:14px;border-top:1px dashed var(--line)}
.plan li:before{content:"";position:absolute;left:2px;top:13px;width:13px;height:8px;border-left:2px solid var(--brand);border-bottom:2px solid var(--brand);transform:rotate(-45deg)}
.plan .btn{margin-top:auto;justify-content:center}

/* ---------- 文章 / 支柱页 ---------- */
.article{padding:36px 0 56px}
.article .wrap{max-width:880px}
.crumb{font-size:13px;color:var(--muted);margin-bottom:16px}
.crumb a{color:var(--muted)}.crumb a:hover{color:var(--brand)}
.article h1{font-size:38px;margin:0 0 14px}
.article .lead{font-size:19px;color:var(--muted);margin:0 0 24px;line-height:1.7}
.article figure{margin:24px 0}
.article h2{font-size:27px;margin:38px 0 12px;padding-top:8px}
.article h3{font-size:21px;margin:28px 0 10px;color:#37405c}
.article p{font-size:16.5px;color:var(--body)}
.article ul,.article ol{margin:0 0 1.1em 1.3em;color:var(--body)}
.article li{margin:6px 0}
/* GEO 答案块 callout */
.answer{background:linear-gradient(180deg,#f4f7ff,#fbfcff);border:1px solid #e1e9ff;border-left:4px solid var(--brand);
  border-radius:10px;padding:13px 18px;margin:0 0 16px;color:#34406b;font-size:16px}
.sources{font-size:13.5px;color:var(--muted);background:var(--bg-soft);border-radius:10px;padding:12px 16px;margin:22px 0}
.sources a{color:var(--brand);word-break:break-all}
.related{display:flex;flex-wrap:wrap;gap:8px 16px;font-size:14px}
.toc{background:var(--bg-soft);border:1px solid var(--line);border-radius:12px;padding:18px 22px;margin:0 0 28px}
.toc strong{display:block;margin-bottom:8px;color:var(--ink)}
.toc a{display:inline-block;margin:3px 14px 3px 0;color:var(--muted);font-size:14px}

/* FAQ 手风琴 */
.faq{margin-top:14px}
.faq h2{margin-bottom:14px}
details{border:1px solid var(--line);border-radius:12px;padding:0;margin:0 0 10px;background:#fff;overflow:hidden}
details summary{cursor:pointer;list-style:none;padding:16px 20px;font-weight:600;color:var(--ink);font-size:16px;
  display:flex;justify-content:space-between;align-items:center}
details summary::-webkit-details-marker{display:none}
details summary:after{content:"+";color:var(--brand);font-size:22px;font-weight:400;margin-left:14px}
details[open] summary:after{content:"\2212"}
details[open] summary{border-bottom:1px solid var(--line)}
details .ans{padding:14px 20px;color:var(--muted);font-size:15px}

/* ---------- 工具页 ---------- */
.tool-box{background:#fff;border:1px solid var(--line);border-radius:16px;box-shadow:var(--shadow-s);padding:28px;margin:24px 0}
.tool-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(150px,1fr));gap:14px}
.tool-grid .it{background:var(--bg-soft);border:1px solid var(--line);border-radius:10px;padding:14px}
.tool-grid .it b{display:block;color:var(--ink);font-size:13px}
.tool-grid .it span{font-size:13px;color:var(--muted);word-break:break-all}
.score{font-size:46px;font-weight:800;color:var(--brand)}
table.dt{width:100%;border-collapse:collapse;font-size:14px;margin:18px 0}
table.dt th,table.dt td{border:1px solid var(--line);padding:10px 12px;text-align:left}
table.dt th{background:var(--bg-soft);color:var(--ink)}
.field{display:flex;gap:10px;flex-wrap:wrap;align-items:center;margin:14px 0}
.field input,.field select{padding:10px 12px;border:1px solid var(--line2);border-radius:8px;font-size:15px;min-width:120px}
.btn.go{cursor:pointer}

/* ---------- 下载页 ---------- */
.dl-os{display:grid;grid-template-columns:repeat(3,1fr);gap:20px;margin:26px 0}
.dl-os .os{background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:26px;text-align:center}
.dl-os .os svg{width:46px;height:46px;margin:0 auto 12px;color:var(--brand)}
.dl-os .os h3{font-size:18px;margin:0 0 4px}
.dl-os .os p{color:var(--muted);font-size:13px;margin:0 0 16px}

/* ---------- 通用 CTA 区 ---------- */
.ctaband{background:linear-gradient(135deg,#3370ff,#5756ff);border-radius:20px;padding:44px;text-align:center;color:#fff;margin:8px 0}
.ctaband h2{color:#fff;font-size:30px;margin:0 0 10px}
.ctaband p{color:rgba(255,255,255,.9);margin:0 0 22px;font-size:17px}
.ctaband .btn{background:#fff;color:var(--brand);box-shadow:none}
.ctaband .btn:hover{background:#f0f4ff}
.check-list{list-style:none;padding:0;margin:0;display:grid;gap:12px}
.check-list li{padding-left:30px;position:relative;color:var(--body)}
.check-list li:before{content:"";position:absolute;left:4px;top:8px;width:14px;height:9px;border-left:2.5px solid var(--brand);border-bottom:2.5px solid var(--brand);transform:rotate(-45deg)}

/* ---------- 页脚 ---------- */
.site-ft{background:#1b2440;color:#aeb6cc;margin-top:64px;padding:48px 0 30px}
.site-ft .cols{display:flex;justify-content:space-between;gap:40px;flex-wrap:wrap}
.ftbrand{display:flex;align-items:center;gap:12px}
.ftbrand strong{color:#fff;font-size:18px}
.fttag{color:#8b94b0;font-size:13px;margin:4px 0 0;max-width:280px}
.site-ft .related{max-width:640px;justify-content:flex-end}
.site-ft .related a{color:#aeb6cc}
.site-ft .related a:hover{color:#fff}
.ftnote{border-top:1px solid #2c3656;margin-top:28px;padding-top:18px;font-size:13px;color:#79839f}

/* ---------- 响应式 ---------- */
@media(max-width:920px){
  .hero .wrap{grid-template-columns:1fr}.hero-art{min-height:340px;order:-1}
  .grid.g3,.price-grid{grid-template-columns:1fr 1fr}.stats{grid-template-columns:1fr 1fr}
  .hero h1{font-size:36px}.sec-head h2{font-size:27px}
}
@media(max-width:600px){
  .nav{display:none}.grid.g3,.grid.g2,.price-grid,.dl-os,.stats{grid-template-columns:1fr}
  .hero h1{font-size:30px}.hero .sub{font-size:22px}.article h1{font-size:29px}
  .site-ft .cols{flex-direction:column}.site-ft .related{justify-content:flex-start}
}