/* === RESET === */
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0;border:0;font:inherit;vertical-align:baseline}
html{scroll-behavior:smooth;text-size-adjust:100%;-webkit-text-size-adjust:100%}
body{min-height:100vh;line-height:1.6;font-family:'Inter','Noto Sans SC','PingFang SC','Microsoft YaHei',sans-serif;font-weight:400;color:#1a1a2e;background:#f2f4f8;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale}
ul,ol{list-style:none}
a{text-decoration:none;color:inherit}
img{max-width:100%;display:block}
button{cursor:pointer;background:none;font:inherit}
:focus-visible{outline:2px solid #0a2540;outline-offset:2px;border-radius:2px}

/* === CSS VARIABLES === */
:root{
  --primary:#0a2540;
  --secondary:#f5c518;
  --accent:#ff6b35;
  --bg:#f2f4f8;
  --surface:#ffffff;
  --text-primary:#1a1a2e;
  --text-secondary:#5a5a7a;
  --border:#d0d4de;
  --shadow:rgba(10,37,64,0.15);
  --header-bg:#0a2540;
  --footer-bg:#071b2e;
  --max-width:1280px;
  --nav-gap:1.5rem;
  --transition:0.3s cubic-bezier(0.25,0.46,0.45,0.94);
  --font-heading:800 clamp(2.5rem,5vw,4rem)/1.1 'Inter','Noto Sans SC','PingFang SC','Microsoft YaHei',sans-serif;
  --font-body:400 1rem/1.6 'Inter','Noto Sans SC','PingFang SC','Microsoft YaHei',sans-serif;
  --font-small:300 0.875rem/1.5 'Inter','Noto Sans SC','PingFang SC','Microsoft YaHei',sans-serif;
}

/* === SKIP LINK === */
.skip-link{
  position:fixed;top:-100%;left:1rem;z-index:10000;
  padding:0.75rem 1.5rem;background:#0a2540;color:#fff;border-radius:0 0 4px 4px;
  font-size:0.875rem;font-weight:600;transition:top 0.25s ease
}
.skip-link:focus{top:0}

/* === HEADER === */
.site-header{
  position:sticky;top:0;z-index:1000;
  background:var(--header-bg);color:#fff;
  box-shadow:0 2px 12px var(--shadow);
  padding:0 1.5rem
}
.header-container{
  max-width:var(--max-width);margin:0 auto;
  display:flex;align-items:center;justify-content:space-between;
  min-height:4rem;gap:1rem
}
.brand{flex-shrink:0}
.brand-link{
  display:flex;align-items:center;gap:0.5rem;
  color:#fff;transition:opacity var(--transition)
}
.brand-link:hover{opacity:0.85}
.brand-name{
  font-weight:800;font-size:1.5rem;letter-spacing:0.02em;
  color:var(--secondary)
}
.brand-accent{
  display:block;width:0.75rem;height:0.75rem;
  background:var(--secondary);
  clip-path:polygon(0 0,100% 0,100% 100%,0 70%);
  transform:rotate(8deg);flex-shrink:0
}
.nav-toggle{display:none;flex-direction:column;gap:5px;padding:0.5rem;border:none;background:none;cursor:pointer}
.nav-toggle-line{display:block;width:1.5rem;height:2px;background:#fff;border-radius:1px;transition:transform var(--transition),opacity var(--transition)}
.nav{flex:1;display:flex;justify-content:flex-end}
.nav-list{display:flex;align-items:center;gap:var(--nav-gap)}
.nav-link{
  position:relative;display:inline-block;
  font-size:0.9375rem;font-weight:500;letter-spacing:0.01em;
  color:rgba(255,255,255,0.85);padding:0.25rem 0;
  transition:color var(--transition)
}
.nav-link::after{
  content:'';position:absolute;left:0;bottom:-2px;
  width:0;height:2px;background:var(--secondary);
  transition:width var(--transition)
}
.nav-link:hover,.nav-link:focus-visible{color:#fff}
.nav-link:hover::after,.nav-link:focus-visible::after{width:100%}
.nav-link[aria-current="page"]{color:var(--secondary);font-weight:600}
.nav-link[aria-current="page"]::after{width:100%;background:var(--secondary)}
.header-cta{
  flex-shrink:0;display:inline-flex;align-items:center;gap:0.375rem;
  padding:0.5rem 1.25rem;border-radius:999px;
  background:var(--accent);color:#fff;
  font-size:0.875rem;font-weight:600;letter-spacing:0.02em;
  white-space:nowrap;transition:background var(--transition),transform var(--transition),box-shadow var(--transition)
}
.header-cta:hover,.header-cta:focus-visible{
  background:#e55a2b;transform:translateY(-1px);
  box-shadow:0 4px 14px rgba(255,107,53,0.35)
}

/* === FOOTER === */
.site-footer{
  background:var(--footer-bg);color:rgba(255,255,255,0.85);
  padding:3rem 1.5rem 2rem;margin-top:4rem
}
.footer-container{
  max-width:var(--max-width);margin:0 auto;
  display:grid;grid-template-columns:1fr 1fr;
  gap:2rem 3rem
}
.footer-brand-link{
  display:inline-block;font-weight:800;font-size:1.375rem;
  color:var(--secondary);margin-bottom:0.375rem;
  transition:opacity var(--transition)
}
.footer-brand-link:hover{opacity:0.8}
.footer-tagline{font-size:0.8125rem;color:rgba(255,255,255,0.55);margin-top:0.25rem}
.footer-links{display:flex;flex-direction:column;gap:0.625rem;align-items:flex-end}
.footer-link{
  font-size:0.9375rem;font-weight:500;
  color:rgba(255,255,255,0.75);
  transition:color var(--transition)
}
.footer-link:hover,.footer-link:focus-visible{color:var(--secondary)}
.footer-info{
  grid-column:1 / -1;display:flex;flex-wrap:wrap;gap:1rem 2rem;
  padding-top:1.25rem;border-top:1px solid rgba(255,255,255,0.1);
  font-size:0.875rem;color:rgba(255,255,255,0.6)
}
.footer-contact{white-space:nowrap}
.footer-addr{color:rgba(255,255,255,0.45);font-size:0.8125rem}
.footer-bottom{
  grid-column:1 / -1;display:flex;flex-wrap:wrap;justify-content:space-between;align-items:center;
  padding-top:1rem;border-top:1px solid rgba(255,255,255,0.08);
  font-size:0.8125rem;color:rgba(255,255,255,0.5)
}
.footer-icp{letter-spacing:0.02em}
.footer-copyright{letter-spacing:0.01em}

/* === SCROLL PROGRESS === */
.scroll-progress{
  position:fixed;top:0;left:0;z-index:9999;
  height:3px;background:var(--secondary);
  width:0%;transition:width 0.1s linear;
  pointer-events:none
}
@media(prefers-reduced-motion:reduce){.scroll-progress{display:none}}

/* === BACK TO TOP === */
.back-to-top{
  position:fixed;bottom:2rem;right:2rem;z-index:999;
  width:2.75rem;height:2.75rem;border-radius:50%;
  background:var(--accent);color:#fff;
  display:flex;align-items:center;justify-content:center;
  font-size:1.25rem;box-shadow:0 4px 12px rgba(255,107,53,0.3);
  opacity:0;visibility:hidden;
  transform:translateY(1rem);
  transition:opacity var(--transition),visibility var(--transition),transform var(--transition),background var(--transition)
}
.back-to-top.visible{opacity:1;visibility:visible;transform:translateY(0)}
.back-to-top:hover,.back-to-top:focus-visible{background:#e55a2b;transform:translateY(-2px)}
.back-to-top::before{content:'↑';font-weight:700;line-height:1}
@media(prefers-reduced-motion:reduce){.back-to-top{transition:none}}

/* === RESPONSIVE === */
@media(max-width:768px){
  .header-container{min-height:3.5rem}
  .nav-toggle{display:flex}
  .nav{
    position:absolute;top:100%;left:0;right:0;
    background:var(--header-bg);
    padding:0 1.5rem 1.25rem;
    flex-direction:column;align-items:stretch;
    display:none;box-shadow:0 8px 20px rgba(0,0,0,0.2)
  }
  .nav[data-open]{display:flex}
  .nav-list{flex-direction:column;align-items:stretch;gap:0}
  .nav-item{border-bottom:1px solid rgba(255,255,255,0.08)}
  .nav-link{display:block;padding:0.75rem 0;font-size:1rem}
  .nav-link::after{display:none}
  .nav-link[aria-current="page"]{color:var(--secondary)}
  .header-cta{font-size:0.8125rem;padding:0.375rem 1rem;white-space:nowrap}
  .site-footer{padding:2rem 1.25rem 1.5rem}
  .footer-container{grid-template-columns:1fr;gap:1.5rem}
  .footer-links{align-items:flex-start}
  .footer-info{flex-direction:column;gap:0.5rem}
  .footer-bottom{flex-direction:column;gap:0.375rem;align-items:flex-start}
  .back-to-top{bottom:1.25rem;right:1.25rem;width:2.5rem;height:2.5rem;font-size:1.125rem}
}

@media(max-width:480px){
  .header-container{gap:0.5rem}
  .brand-name{font-size:1.25rem}
  .brand-accent{width:0.625rem;height:0.625rem}
  .header-cta{font-size:0.75rem;padding:0.25rem 0.75rem}
  .nav-link{padding:0.625rem 0;font-size:0.9375rem}
}

@media(min-width:769px){
  .nav{display:flex!important;position:static;background:transparent;padding:0;box-shadow:none}
  .nav-toggle{display:none!important}
}

/* === UTILITY === */
.container{max-width:var(--max-width);margin:0 auto;padding:0 1.5rem}
.sr-only{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}