/* ============================================
   Tangzhi Common CSS - Shared across all pages
   ============================================ */

/* ===== SKIP LINK (Accessibility) ===== */
.skip-link{position:absolute;top:-100px;left:0;background:var(--primary);color:#fff;padding:12px 24px;z-index:9999;font-weight:600;font-size:15px;transition:top .3s}
.skip-link:focus{top:0}

/* RESET & BASE */
*{margin:0;padding:0;box-sizing:border-box}
:root{
  --primary:#2563eb;
  --primary-dark:#1d4ed8;
  --primary-light:#3b82f6;
  --dark:#0f172a;
  --dark2:#1e293b;
  --dark3:#334155;
  --light:#f8fafc;
  --gray:#94a3b8;
  --gray2:#cbd5e1;
  --white:#ffffff;
  --orange:#f59e0b;
  --green:#10b981;
  --gradient:linear-gradient(135deg,#2563eb,#7c3aed)
}
html{scroll-behavior:smooth}
body{font-family:-apple-system,BlinkMacSystemFont,'Segoe UI','PingFang SC','Hiragino Sans GB','Microsoft YaHei',sans-serif;color:var(--dark);line-height:1.6;overflow-x:hidden}
a{text-decoration:none;color:inherit}
ul{list-style:none}

/* ===== NAV ===== */
.nav{position:fixed;top:0;left:0;right:0;z-index:1000;padding:20px 0;transition:all .3s}
.nav.scrolled{background:rgba(15,23,42,.95);backdrop-filter:blur(20px);padding:12px 0;box-shadow:0 4px 30px rgba(0,0,0,.15)}
.nav-inner{max-width:1200px;margin:0 auto;padding:0 24px;display:flex;align-items:center;justify-content:space-between}
.nav-logo{display:flex;align-items:center;gap:10px;font-size:20px;font-weight:700;color:var(--white)}
.nav-logo .logo-icon{width:36px;height:36px;background:var(--gradient);border-radius:10px;display:flex;align-items:center;justify-content:center;font-size:18px;color:#fff;font-weight:800}
.nav-menu{display:flex;gap:32px;align-items:center}
.nav-menu a{color:rgba(255,255,255,.75);font-size:15px;font-weight:500;transition:color .3s;position:relative}
.nav-menu a:hover,.nav-menu a.active{color:#fff}
.nav-menu a::after{content:'';position:absolute;bottom:-4px;left:0;width:0;height:2px;background:var(--gradient);transition:width .3s}
.nav-menu a:hover::after,.nav-menu a.active::after{width:100%}
.nav-cta{background:var(--gradient);color:#fff!important;padding:10px 24px;border-radius:8px;font-weight:600;font-size:14px;transition:transform .3s,box-shadow .3s}
.nav-cta::after{display:none!important}
.nav-cta:hover{transform:translateY(-2px);box-shadow:0 8px 25px rgba(37,99,235,.4)}
.hamburger{display:none;flex-direction:column;gap:5px;cursor:pointer;padding:5px}
.hamburger span{width:24px;height:2px;background:#fff;transition:all .3s}

/* Nav variant: always solid (for sub pages) */
.nav-solid{background:rgba(15,23,42,.95);backdrop-filter:blur(20px);box-shadow:0 4px 30px rgba(0,0,0,.15)}

/* ===== BUTTONS ===== */
.btn-primary{background:var(--gradient);color:#fff;padding:16px 36px;border-radius:12px;font-size:16px;font-weight:600;border:none;cursor:pointer;transition:all .3s;display:inline-flex;align-items:center;gap:8px;font-family:inherit}
.btn-primary:hover{transform:translateY(-3px);box-shadow:0 12px 35px rgba(37,99,235,.4)}
.btn-outline{background:transparent;color:#fff;padding:16px 36px;border-radius:12px;font-size:16px;font-weight:600;border:1px solid rgba(255,255,255,.2);cursor:pointer;transition:all .3s;font-family:inherit}
.btn-outline:hover{background:rgba(255,255,255,.05);border-color:rgba(255,255,255,.4)}

/* ===== PAGE HERO (Sub pages) ===== */
.page-hero{padding:140px 24px 80px;background:var(--dark);position:relative;overflow:hidden}
.page-hero-bg{position:absolute;inset:0;background:radial-gradient(ellipse at 30% 50%,rgba(37,99,235,.12),transparent 60%),radial-gradient(ellipse at 70% 80%,rgba(124,58,237,.08),transparent 50%)}
.page-hero-grid{position:absolute;inset:0;background-image:linear-gradient(rgba(255,255,255,.025) 1px,transparent 1px),linear-gradient(90deg,rgba(255,255,255,.025) 1px,transparent 1px);background-size:60px 60px}
.page-hero-inner{max-width:1200px;margin:0 auto;position:relative;z-index:2}
.breadcrumb{display:flex;align-items:center;gap:8px;font-size:14px;color:rgba(255,255,255,.5);margin-bottom:24px}
.breadcrumb a{color:rgba(255,255,255,.5);transition:color .3s}
.breadcrumb a:hover{color:#fff}
.breadcrumb span{color:rgba(255,255,255,.3)}
.page-hero h1{font-size:clamp(32px,4vw,52px);font-weight:800;color:#fff;margin-bottom:16px;letter-spacing:-1px}
.page-hero p{font-size:17px;color:var(--gray);max-width:520px}

/* ===== FOOTER ===== */
.footer{background:var(--dark);padding:60px 24px 32px;margin-top:0}
.footer-inner{max-width:1200px;margin:0 auto}
.footer-grid{display:grid;grid-template-columns:2fr 1fr 1fr 1fr;gap:48px;margin-bottom:48px}
.footer-brand .nav-logo{margin-bottom:16px}
.footer-brand p{font-size:14px;color:var(--gray);line-height:1.8;margin-top:12px;max-width:280px}
.footer-col h4{font-size:15px;font-weight:700;color:#fff;margin-bottom:20px}
.footer-col ul li{margin-bottom:10px}
.footer-col ul li a{font-size:14px;color:var(--gray);transition:color .3s}
.footer-col ul li a:hover{color:#fff}
.footer-bottom{border-top:1px solid rgba(255,255,255,.06);padding-top:28px;display:flex;justify-content:space-between;align-items:center;flex-wrap:wrap;gap:16px}
.footer-bottom p{font-size:13px;color:rgba(255,255,255,.35)}

/* ===== FADE ANIMATION ===== */
.fade-up{opacity:0;transform:translateY(30px);transition:opacity .6s ease,transform .6s ease}
.fade-up.visible{opacity:1;transform:translateY(0)}

/* ===== RESPONSIVE ===== */
@media(max-width:900px){
  .footer-grid{grid-template-columns:1fr 1fr}
}
@media(max-width:768px){
  .nav-menu{display:none;position:absolute;top:100%;left:0;right:0;background:rgba(15,23,42,.98);flex-direction:column;gap:0;padding:20px}
  .nav-menu.open{display:flex}
  .nav-menu a{padding:14px 24px;border-bottom:1px solid rgba(255,255,255,.05);width:100%}
  .nav-menu a::after{display:none}
  .hamburger{display:flex}
  .footer-grid{grid-template-columns:1fr}
  .footer-bottom{flex-direction:column;text-align:center}
  .page-hero{padding:120px 24px 60px}
  .page-hero h1{font-size:28px}
}