:root{
  --ink:#2a2f45;
  --ink-soft:#636a83;
  --paper:#f3f4ff;
  --white:#ffffff;
  --glass:rgba(255,255,255,.55);
  --glass-border:rgba(255,255,255,.7);
  --brand:#6366f1;
  --brand-deep:#4f46e5;
  --brand-soft:rgba(99,102,241,.12);
  --accent:#a855f7;
  --line:rgba(99,102,241,.12);
  --shadow:0 10px 30px rgba(63,70,160,.08);
  --serif:"Noto Serif SC","Songti SC","STSong","SimSun",serif;
  --sans:"PingFang SC","Microsoft YaHei","Hiragino Sans GB",sans-serif;
}
*{margin:0;padding:0;box-sizing:border-box;}
html{scroll-behavior:smooth;}
body{
  font-family:var(--sans);color:var(--ink);line-height:1.8;font-size:16px;
  -webkit-font-smoothing:antialiased;
  background:
    radial-gradient(600px circle at 12% 8%, rgba(129,140,248,.18), transparent 45%),
    radial-gradient(700px circle at 88% 30%, rgba(168,85,247,.14), transparent 45%),
    radial-gradient(600px circle at 40% 95%, rgba(56,189,248,.14), transparent 45%),
    var(--paper);
  background-attachment:fixed;
}

/* 顶栏 */
header{
  position:fixed;top:0;left:0;right:0;z-index:100;
  background:rgba(243,244,255,.75);backdrop-filter:blur(14px);
  border-bottom:1px solid var(--line);-webkit-backdrop-filter:blur(14px);
}
.nav{max-width:1140px;margin:0 auto;display:flex;align-items:center;justify-content:space-between;padding:13px 24px;}
.brand{display:flex;align-items:center;gap:10px;font-weight:700;font-size:20px;color:var(--ink);text-decoration:none;letter-spacing:1px;font-family:var(--serif);}
.brand .logo{width:34px;height:34px;border-radius:9px;display:inline-flex;align-items:center;justify-content:center;color:#fff;font-size:17px;background:linear-gradient(135deg,var(--brand),var(--brand-deep));box-shadow:0 3px 10px rgba(99,102,241,.35);}
.back-link{
  display:inline-flex;align-items:center;gap:8px;color:var(--ink-soft);text-decoration:none;
  font-size:15px;transition:color .2s;
}
.back-link:hover{color:var(--brand-deep);}

/* 主副标题 */
.page-hero{position:relative;padding:150px 24px 70px;text-align:center;}
.page-hero .kicker{font-size:13px;letter-spacing:4px;color:var(--brand);margin-bottom:16px;}
.page-hero h1{font-family:var(--serif);font-size:clamp(32px,5.5vw,54px);font-weight:900;letter-spacing:3px;color:var(--ink);}
.page-hero .sub{margin:18px auto 0;font-size:17px;color:var(--ink-soft);max-width:640px;}
.page-hero .crumb{max-width:1140px;margin:0 auto;display:flex;flex-wrap:wrap;gap:8px;justify-content:center;margin-top:26px;font-size:13px;color:var(--ink-soft);}
.page-hero .crumb a{color:var(--brand);text-decoration:none;}
.page-hero .crumb a:hover{text-decoration:underline;}

/* 内容区 */
section{max-width:1080px;margin:0 auto;padding:30px 24px;}
.glass-card{
  background:var(--glass);backdrop-filter:blur(12px);-webkit-backdrop-filter:blur(12px);
  border:1px solid var(--glass-border);border-radius:16px;box-shadow:var(--shadow);
  padding:30px 34px;margin-bottom:26px;
}
.glass-card h2{font-family:var(--serif);font-size:24px;letter-spacing:1px;margin-bottom:16px;color:var(--ink);border-left:4px solid var(--brand);padding-left:14px;}
.glass-card h3{font-size:18px;margin:20px 0 10px;color:var(--ink);}
.glass-card p{color:var(--ink-soft);margin-bottom:10px;}
.glass-card ul,.glass-card ol{margin:6px 0 12px 22px;color:var(--ink-soft);}
.glass-card li{margin-bottom:7px;}
.glass-card code{
  background:var(--brand-soft);color:var(--brand-deep);border-radius:6px;
  padding:2px 8px;font-family:Consolas,Monaco,monospace;font-size:.9em;
}
.glass-card .hl{border-left:3px solid var(--accent);background:rgba(168,85,247,.07);padding:12px 16px;border-radius:8px;margin:14px 0;color:var(--ink);font-size:15px;}

/* 章节索引卡 */
.toc{display:flex;flex-wrap:wrap;gap:12px;list-style:none;margin:6px 0 6px;padding:0;}
.toc li a{
  display:inline-block;background:var(--brand-soft);color:var(--brand-deep);text-decoration:none;
  padding:7px 16px;border-radius:24px;font-size:14px;transition:background .2s;
}
.toc li a:hover{background:var(--brand);color:#fff;}

/* 相关专题 */
.related{max-width:1080px;margin:40px auto;padding:0 24px;}
.related h2{font-family:var(--serif);font-size:22px;letter-spacing:1px;margin-bottom:18px;}
.related-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:18px;}
.rel-card{
  display:block;background:var(--glass);backdrop-filter:blur(12px);-webkit-backdrop-filter:blur(12px);
  border:1px solid var(--glass-border);border-radius:14px;box-shadow:var(--shadow);
  padding:20px 22px;text-decoration:none;color:var(--ink);transition:transform .2s,box-shadow .2s;
}
.rel-card:hover{transform:translateY(-4px);box-shadow:0 14px 30px rgba(63,70,160,.13);}
.rel-card h3{font-size:16px;margin-bottom:6px;}
.rel-card p{font-size:13px;color:var(--ink-soft);}

/* 页脚 + 备案号 */
footer{background:#23223a;color:#9b98b8;padding:40px 24px 30px;margin-top:60px;}
.footer-inner{max-width:1140px;margin:0 auto;display:flex;flex-wrap:wrap;gap:30px;justify-content:space-between;}
.footer-brand{max-width:300px;}
.footer-brand .brand{color:#fff;margin-bottom:12px;}
.footer-brand .brand .logo{background:linear-gradient(135deg,#818cf8,#6366f1);}
.footer-brand p{font-size:13px;line-height:1.9;}
.footer-notes a{color:#8f8cb0;text-decoration:none;font-size:13px;margin-right:16px;transition:color .2s;}
.footer-notes a:hover{color:#c7d2fe;}
.footer-bottom{
  max-width:1140px;margin:26px auto 0;border-top:1px solid rgba(255,255,255,.08);
  padding-top:18px;display:flex;flex-wrap:wrap;gap:12px;justify-content:space-between;align-items:center;
  font-size:12.5px;color:#7a78a0;
}
.footer-bottom a{color:#8f8cb0;text-decoration:none;}
.footer-bottom a:hover{color:#c7d2fe;}
.footer-bottom .icp{letter-spacing:1px;}

/* 步骤标签 */
.step-chip{display:inline-flex;align-items:center;justify-content:center;width:26px;height:26px;border-radius:50%;background:linear-gradient(135deg,var(--brand),var(--accent));color:#fff;font-size:14px;font-weight:700;margin-right:10px;}

@media(max-width:880px){
  .related-grid{grid-template-columns:1fr;}
  section{padding:20px 18px;}
}
.fade-in{opacity:0;transform:translateY(22px);transition:opacity .7s ease,transform .7s ease;}
.fade-in.visible{opacity:1;transform:none;}