*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
:root{--primary:#1e88e5;--primary-dark:#1565c0;--accent:#42a5f5;--bg:#f5f8fc;--card:#fff;--text:#1a1a2e;--text-light:#5a6270;--border:#e3eaf2;--shadow:0 2px 12px rgba(30,136,229,.08);--radius:12px;--max:1200px}
html{scroll-behavior:smooth;font-size:16px}
body{font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Hiragino Sans GB","Microsoft YaHei",sans-serif;color:var(--text);background:var(--bg);line-height:1.75;-webkit-font-smoothing:antialiased}
a{color:var(--primary);text-decoration:none;transition:color .2s}
a:hover{color:var(--primary-dark)}
img{max-width:100%;height:auto;display:block}
.container{max-width:var(--max);margin:0 auto;padding:0 20px}

/* Header */
.site-header{background:var(--card);border-bottom:1px solid var(--border);position:sticky;top:0;z-index:100;box-shadow:var(--shadow)}
.header-inner{display:flex;align-items:center;justify-content:space-between;height:64px}
.logo{display:flex;align-items:center;gap:10px;font-weight:700;font-size:1.15rem;color:var(--text)}
.logo img{width:40px;height:40px;border-radius:10px}
.nav{display:flex;gap:6px}
.nav a{padding:8px 16px;border-radius:8px;color:var(--text-light);font-size:.95rem;font-weight:500}
.nav a:hover,.nav a.active{background:rgba(30,136,229,.08);color:var(--primary)}
.menu-toggle{display:none;background:none;border:none;cursor:pointer;padding:8px}
.menu-toggle span{display:block;width:22px;height:2px;background:var(--text);margin:5px 0;transition:.3s}

/* Hero */
.hero{background:linear-gradient(135deg,#1e88e5 0%,#42a5f5 50%,#64b5f6 100%);color:#fff;padding:60px 0 80px;text-align:center}
.hero h1{font-size:2rem;margin-bottom:16px;line-height:1.35}
.hero p{font-size:1.05rem;opacity:.92;max-width:720px;margin:0 auto 28px}
.btn-group{display:flex;gap:14px;justify-content:center;flex-wrap:wrap}
.btn{display:inline-flex;align-items:center;gap:8px;padding:13px 28px;border-radius:50px;font-weight:600;font-size:1rem;border:none;cursor:pointer;transition:transform .2s,box-shadow .2s}
.btn:hover{transform:translateY(-2px)}
.btn-primary{background:#fff;color:var(--primary);box-shadow:0 4px 16px rgba(0,0,0,.12)}
.btn-outline{background:transparent;color:#fff;border:2px solid rgba(255,255,255,.7)}
.btn-outline:hover{background:rgba(255,255,255,.15)}

/* Sections */
.section{padding:56px 0}
.section-title{text-align:center;margin-bottom:40px}
.section-title h2{font-size:1.65rem;margin-bottom:10px;color:var(--text)}
.section-title p{color:var(--text-light);max-width:640px;margin:0 auto}
.section-alt{background:var(--card)}

/* Cards Grid */
.grid{display:grid;gap:24px}
.grid-2{grid-template-columns:repeat(2,1fr)}
.grid-3{grid-template-columns:repeat(3,1fr)}
.grid-4{grid-template-columns:repeat(4,1fr)}
.card{background:var(--card);border-radius:var(--radius);overflow:hidden;box-shadow:var(--shadow);border:1px solid var(--border);transition:transform .25s,box-shadow .25s}
.card:hover{transform:translateY(-4px);box-shadow:0 8px 24px rgba(30,136,229,.12)}
.card-img{aspect-ratio:9/16;overflow:hidden;background:#eef2f7;max-height:360px}
.card-img img{width:100%;height:100%;object-fit:cover;object-position:top}
.card-body{padding:20px}
.card-body h3{font-size:1.05rem;margin-bottom:8px}
.card-body p{font-size:.9rem;color:var(--text-light)}

/* Feature blocks */
.feature-row{display:grid;grid-template-columns:1fr 1fr;gap:40px;align-items:center;margin-bottom:48px}
.feature-row.reverse{direction:rtl}
.feature-row.reverse>*{direction:ltr}
.feature-img{border-radius:var(--radius);overflow:hidden;box-shadow:var(--shadow);max-width:320px;margin:0 auto}
.feature-text h3{font-size:1.3rem;margin-bottom:14px;color:var(--primary-dark)}
.feature-text p{margin-bottom:12px;color:var(--text-light)}
.feature-text ul{padding-left:20px;color:var(--text-light)}
.feature-text li{margin-bottom:6px}

/* Steps */
.steps{counter-reset:step}
.step{display:flex;gap:20px;margin-bottom:28px;align-items:flex-start}
.step-num{flex-shrink:0;width:44px;height:44px;background:var(--primary);color:#fff;border-radius:50%;display:flex;align-items:center;justify-content:center;font-weight:700;font-size:1.1rem}
.step-content h4{font-size:1.05rem;margin-bottom:6px}
.step-content p{color:var(--text-light);font-size:.95rem}

/* Content article */
.article{max-width:860px;margin:0 auto}
.article h2{font-size:1.4rem;margin:36px 0 14px;padding-bottom:8px;border-bottom:2px solid var(--accent);color:var(--primary-dark)}
.article h3{font-size:1.15rem;margin:24px 0 10px}
.article p{margin-bottom:14px;color:var(--text-light)}
.article ul,.article ol{margin:0 0 16px 24px;color:var(--text-light)}
.article li{margin-bottom:6px}
.article img{border-radius:var(--radius);margin:20px auto;box-shadow:var(--shadow);max-width:320px}

/* FAQ */
.faq-item{background:var(--card);border:1px solid var(--border);border-radius:var(--radius);margin-bottom:12px;overflow:hidden}
.faq-q{padding:16px 20px;font-weight:600;cursor:pointer;display:flex;justify-content:space-between;align-items:center}
.faq-q::after{content:"+";font-size:1.3rem;color:var(--primary);transition:transform .3s}
.faq-item.open .faq-q::after{transform:rotate(45deg)}
.faq-a{padding:0 20px;max-height:0;overflow:hidden;transition:max-height .35s,padding .35s;color:var(--text-light);font-size:.95rem}
.faq-item.open .faq-a{padding:0 20px 16px;max-height:300px}

/* Breadcrumb */
.breadcrumb{padding:16px 0;font-size:.88rem;color:var(--text-light)}
.breadcrumb a{color:var(--text-light)}
.breadcrumb a:hover{color:var(--primary)}
.breadcrumb span{margin:0 8px}

/* Page header */
.page-header{background:linear-gradient(135deg,var(--primary),var(--accent));color:#fff;padding:48px 0;text-align:center}
.page-header h1{font-size:1.75rem;margin-bottom:8px}
.page-header p{opacity:.88}

/* Footer */
.site-footer{background:#1a2332;color:#b0bec5;padding:48px 0 24px;margin-top:60px}
.footer-grid{display:grid;grid-template-columns:2fr 1fr 1fr 1fr;gap:32px;margin-bottom:32px}
.footer-brand img{width:48px;border-radius:10px;margin-bottom:12px}
.footer-brand p{font-size:.9rem;line-height:1.7}
.footer-col h4{color:#fff;margin-bottom:14px;font-size:.95rem}
.footer-col a{display:block;color:#90a4ae;font-size:.88rem;margin-bottom:8px}
.footer-col a:hover{color:#fff}
.footer-bottom{border-top:1px solid #2c3e50;padding-top:20px;text-align:center;font-size:.85rem}

/* Error pages */
.error-page{text-align:center;padding:100px 20px}
.error-page h1{font-size:5rem;color:var(--primary);line-height:1}
.error-page h2{margin:16px 0;font-size:1.5rem}
.error-page p{color:var(--text-light);margin-bottom:28px}

/* TOC */
.toc{background:var(--card);border:1px solid var(--border);border-radius:var(--radius);padding:24px;margin-bottom:32px}
.toc h3{font-size:1rem;margin-bottom:12px;color:var(--primary-dark)}
.toc ol{padding-left:20px}
.toc li{margin-bottom:6px;font-size:.92rem}
.toc a{color:var(--text-light)}
.toc a:hover{color:var(--primary)}

/* Responsive */
@media(max-width:992px){
  .grid-3,.grid-4{grid-template-columns:repeat(2,1fr)}
  .footer-grid{grid-template-columns:1fr 1fr}
  .feature-row{grid-template-columns:1fr;text-align:center}
  .feature-row.reverse{direction:ltr}
}
@media(max-width:768px){
  .nav{position:fixed;top:64px;left:0;right:0;background:var(--card);flex-direction:column;padding:16px;border-bottom:1px solid var(--border);transform:translateY(-120%);opacity:0;transition:.3s;box-shadow:var(--shadow)}
  .nav.open{transform:translateY(0);opacity:1}
  .nav a{padding:12px 16px}
  .menu-toggle{display:block}
  .hero{padding:40px 0 56px}
  .hero h1{font-size:1.5rem}
  .grid-2,.grid-3,.grid-4{grid-template-columns:1fr}
  .footer-grid{grid-template-columns:1fr}
  .section{padding:40px 0}
  .card-img{max-height:280px}
}