/* ================================================================
   数智桥 — Shared Styles
   ================================================================ */

/* ----- Reset & Variables ----- */
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
:root{
  --primary:#1a56db;
  --primary-dark:#1e40af;
  --primary-light:#3b82f6;
  --accent:#6366f1;
  --accent-light:#818cf8;
  --bg:#ffffff;
  --bg-alt:#f8fafc;
  --bg-dark:#0f172a;
  --text:#1e293b;
  --text-secondary:#475569;
  --text-muted:#94a3b8;
  --border:#e2e8f0;
  --border-light:#f1f5f9;
  --radius:12px;
  --radius-lg:20px;
  --shadow-sm:0 1px 2px rgba(0,0,0,.05);
  --shadow:0 4px 6px -1px rgba(0,0,0,.06),0 2px 4px -2px rgba(0,0,0,.04);
  --shadow-md:0 8px 20px -4px rgba(0,0,0,.08),0 4px 8px -4px rgba(0,0,0,.04);
  --shadow-lg:0 16px 32px -8px rgba(0,0,0,.1);
  --max-width:1240px;
  --header-h:76px;
}
html{scroll-behavior:smooth;scroll-padding-top:var(--header-h)}
body{
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Helvetica Neue",Arial,"PingFang SC","Hiragino Sans GB","Microsoft YaHei","WenQuanYi Micro Hei",sans-serif;
  color:var(--text);background:var(--bg);
  line-height:1.7;-webkit-font-smoothing:antialiased;
  overflow-x:hidden;
}

/* ----- Header ----- */
.header{
  position:fixed;top:0;left:0;right:0;z-index:100;
  height:var(--header-h);
  display:flex;align-items:center;
  transition:all .35s ease;
  background:transparent;
}
.header.scrolled{
  background:rgba(255,255,255,.92);
  backdrop-filter:blur(20px);
  -webkit-backdrop-filter:blur(20px);
  box-shadow:0 1px 3px rgba(0,0,0,.06);
  border-bottom:1px solid var(--border);
}
.header-inner{
  width:100%;max-width:var(--max-width);
  margin:0 auto;padding:0 48px;
  display:flex;align-items:center;justify-content:space-between;
}
.logo{
  display:flex;align-items:center;gap:12px;
  font-size:24px;font-weight:800;color:#fff;
  text-decoration:none;letter-spacing:.5px;
  transition:color .35s;
}
.header.scrolled .logo{color:var(--text)}
.logo-icon{
  width:42px;height:42px;
  background:linear-gradient(135deg,var(--primary),var(--accent));
  border-radius:11px;
  display:flex;align-items:center;justify-content:center;
  font-size:22px;color:#fff;font-weight:800;
}
.nav{display:flex;align-items:center;gap:40px;list-style:none}
.nav a{
  color:rgba(255,255,255,.82);
  text-decoration:none;font-size:15px;font-weight:500;
  transition:color .3s;position:relative;
  padding:4px 0;
}
.header.scrolled .nav a{color:var(--text-secondary)}
.nav a:hover,.nav a.active{color:#fff}
.header.scrolled .nav a:hover,.nav a.active{color:var(--primary)}
.nav a::after{
  content:'';position:absolute;bottom:-2px;left:0;
  width:0;height:2px;background:var(--primary-light);border-radius:1px;
  transition:width .3s ease;
}
.nav a:hover::after,.nav a.active::after{width:100%}

/* ----- Page Banner (sub-pages) ----- */
.page-banner{
  padding:140px 48px 80px;
  background:linear-gradient(135deg,#0f172a 0%,#1e3a5f 50%,#1a56db 100%);
  text-align:center;color:#fff;position:relative;overflow:hidden;
}
.page-banner::before{
  content:'';position:absolute;inset:0;
  background:radial-gradient(ellipse at 30% 50%,rgba(59,130,246,.12) 0%,transparent 50%),
             radial-gradient(ellipse at 70% 30%,rgba(99,102,241,.08) 0%,transparent 50%);
}
.page-banner-inner{position:relative;z-index:1;max-width:800px;margin:0 auto}
.page-banner h1{
  font-size:clamp(32px,4.5vw,52px);font-weight:800;
  margin-bottom:16px;line-height:1.2;
}
.page-banner h1 span{
  background:linear-gradient(135deg,#60a5fa,#a78bfa);
  -webkit-background-clip:text;-webkit-text-fill-color:transparent;
  background-clip:text;
}
.page-banner p{font-size:17px;color:rgba(255,255,255,.65);max-width:550px;margin:0 auto;line-height:1.8}

/* ----- Footer ----- */
.footer{
  background:var(--bg-dark);color:rgba(255,255,255,.55);
  padding:50px 48px 28px;
}
.footer-inner{max-width:var(--max-width);margin:0 auto}
.footer-grid{display:grid;grid-template-columns:2fr 1fr 1fr 1fr;gap:40px;margin-bottom:36px}
.footer-brand .logo{color:#fff;margin-bottom:14px}
.footer-brand .logo .logo-icon{width:36px;height:36px;font-size:18px;border-radius:9px}
.footer-brand p{font-size:14px;line-height:1.8}
.footer-col h4{color:#fff;font-size:15px;font-weight:600;margin-bottom:18px}
.footer-col ul{list-style:none}
.footer-col li{margin-bottom:10px}
.footer-col a{color:rgba(255,255,255,.45);text-decoration:none;font-size:14px;transition:color .3s}
.footer-col a:hover{color:#fff}
.footer-bottom{
  padding-top:22px;border-top:1px solid rgba(255,255,255,.07);
  font-size:13px;text-align:center;
}

/* ----- Buttons ----- */
.btn{
  display:inline-flex;align-items:center;gap:8px;
  padding:15px 36px;border-radius:50px;
  font-size:16px;font-weight:600;text-decoration:none;
  transition:all .3s ease;cursor:pointer;border:none;
}
.btn-primary{
  background:var(--primary);color:#fff;
  box-shadow:0 4px 18px rgba(26,86,219,.35);
}
.btn-primary:hover{background:var(--primary-dark);transform:translateY(-2px);box-shadow:0 8px 28px rgba(26,86,219,.45)}
.btn-outline{
  background:transparent;color:#fff;
  border:1.5px solid rgba(255,255,255,.3);
}
.btn-outline:hover{background:rgba(255,255,255,.08);border-color:rgba(255,255,255,.5);transform:translateY(-2px)}
.btn-light{background:#fff;color:var(--primary);box-shadow:0 4px 15px rgba(0,0,0,.15)}
.btn-light:hover{background:#f1f5f9;box-shadow:0 8px 25px rgba(0,0,0,.2);transform:translateY(-2px)}
.btn-sm{padding:10px 24px;font-size:14px}

/* ----- Section ----- */
.section{padding:80px 48px}
.section-alt{background:var(--bg-alt)}
.section-dark{background:var(--bg-dark);color:#fff}
.section-inner{max-width:var(--max-width);margin:0 auto}
.section-header{text-align:center;margin-bottom:56px}
.section-label{
  display:inline-block;padding:4px 16px;
  background:rgba(26,86,219,.07);color:var(--primary);
  border-radius:50px;font-size:13px;font-weight:600;
  letter-spacing:2px;text-transform:uppercase;margin-bottom:14px;
}
.section-header h2{font-size:clamp(28px,3.5vw,40px);font-weight:700;margin-bottom:14px;line-height:1.25}
.section-header p{font-size:16px;color:var(--text-secondary);max-width:580px;margin:0 auto}

/* ----- Cards ----- */
.card{
  background:var(--bg);border-radius:var(--radius-lg);
  padding:36px 32px;box-shadow:var(--shadow);
  border:1px solid var(--border);
  transition:all .35s ease;position:relative;overflow:hidden;
}
.card:hover{transform:translateY(-4px);box-shadow:var(--shadow-lg)}
.card-accent::before{
  content:'';position:absolute;top:0;left:0;right:0;height:3px;
  background:linear-gradient(90deg,var(--primary),var(--accent));
}
.card-icon{
  width:52px;height:52px;border-radius:13px;
  display:flex;align-items:center;justify-content:center;
  font-size:24px;margin-bottom:18px;
}
.card-icon.blue{background:#eff6ff;color:var(--primary)}
.card-icon.indigo{background:#eef2ff;color:var(--accent)}
.card-icon.cyan{background:#ecfeff;color:#0891b2}
.card-icon.emerald{background:#ecfdf5;color:#059669}
.card h3{font-size:20px;font-weight:700;margin-bottom:10px}
.card p{font-size:15px;color:var(--text-secondary);line-height:1.75}

/* ----- Tags ----- */
.tags{display:flex;flex-wrap:wrap;gap:8px;margin-top:16px}
.tag{
  padding:4px 12px;background:var(--bg-alt);
  border-radius:50px;font-size:12px;color:var(--text-secondary);
  border:1px solid var(--border);font-weight:500;
}

/* ----- Stats Row ----- */
.stats-row{display:grid;grid-template-columns:repeat(4,1fr);gap:20px}
.stat-item{text-align:center;padding:24px 16px}
.stat-number{font-size:44px;font-weight:800;color:var(--primary);line-height:1;margin-bottom:6px}
.stat-label{font-size:14px;color:var(--text-secondary);font-weight:500}

/* ----- Animations ----- */
@keyframes fadeInUp{from{opacity:0;transform:translateY(30px)}to{opacity:1;transform:translateY(0)}}
.reveal{opacity:0;transform:translateY(40px);transition:all .6s ease}
.reveal.visible{opacity:1;transform:translateY(0)}

/* ----- Two Column ----- */
.two-col{display:grid;grid-template-columns:1fr 1fr;gap:56px;align-items:center}
.two-col h3{font-size:28px;font-weight:700;margin-bottom:20px}
.two-col p{font-size:16px;color:var(--text-secondary);line-height:1.9;margin-bottom:14px}

/* ----- Grid 2/3/4 ----- */
.grid-2{display:grid;grid-template-columns:repeat(2,1fr);gap:24px}
.grid-3{display:grid;grid-template-columns:repeat(3,1fr);gap:24px}
.grid-4{display:grid;grid-template-columns:repeat(4,1fr);gap:24px}

/* ===== Responsive ===== */
@media(max-width:1024px){
  .grid-2,.grid-3,.grid-4{grid-template-columns:repeat(2,1fr)}
  .two-col{grid-template-columns:1fr;gap:40px}
  .footer-grid{grid-template-columns:1fr 1fr}
  .stats-row{grid-template-columns:repeat(2,1fr)}
}
@media(max-width:768px){
  .section{padding:60px 28px}
  .page-banner{padding:120px 28px 60px}
  .header-inner{padding:0 28px}
  .nav{gap:24px}.nav a{font-size:14px}
  .grid-2,.grid-3,.grid-4{grid-template-columns:1fr}
  .footer-grid{grid-template-columns:1fr}
  .two-col h3{font-size:24px}
  .section-header h2{font-size:26px}
}
@media(max-width:480px){
  .section{padding:48px 20px}
  .page-banner{padding:110px 20px 48px}
  .header-inner{padding:0 20px}
  .nav{gap:14px}.nav a{font-size:13px}
  .btn{padding:12px 28px;font-size:15px}
  .logo{font-size:20px}
  .stats-row{grid-template-columns:1fr}
}