/* ========================================
   北京瑞鑫科技 官网
   设计系统：苹果极简 · 0圆角 · 深浅交替
   ======================================== */

/* --- Reset & Base --- */
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
body{
  font-family:"PingFang SC","Hiragino Sans GB","Microsoft YaHei","Helvetica Neue",Arial,sans-serif;
  font-size:17px;line-height:1.588;color:#1d1d1f;
  background:#fff;-webkit-font-smoothing:antialiased;
  overflow-x:hidden;
}
img{max-width:100%;height:auto;display:block}
a{color:#0071e3;text-decoration:none;transition:color .2s}
a:hover{color:#005bb5}

/* --- Utility --- */
.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}

/* --- Section Base --- */
.section{padding:120px 0}
.section-dark{background:#000;color:#fff}
.section-dark a{color:#2997ff}
.section-dark a:hover{color:#6bbfff}
.section-light{background:#fff;color:#1d1d1f}
.section-gray{background:#f5f5f7;color:#1d1d1f}

.container{max-width:1200px;margin:0 auto;padding:0 40px}

.section-title{font-size:48px;font-weight:600;line-height:1.1;letter-spacing:-.015em;margin-bottom:16px}
.section-subtitle{font-size:21px;font-weight:400;line-height:1.33;color:#86868b}
.section-dark .section-subtitle{color:#a1a1a6}

/* --- Navbar --- */
.navbar{
  position:fixed;top:0;left:0;right:0;z-index:1000;
  height:56px;display:flex;align-items:center;
  background:rgba(29,29,31,.85);backdrop-filter:saturate(180%) blur(20px);
  -webkit-backdrop-filter:saturate(180%) blur(20px);
  color:#f5f5f7;font-size:14px;font-weight:400;
  transition:background .3s;
}
.navbar .container{display:flex;align-items:center;justify-content:space-between;width:100%}
.nav-logo{display:flex;align-items:center;gap:8px;font-size:18px;font-weight:600;color:#fff;letter-spacing:-.01em;white-space:nowrap}
.nav-logo img{width:36px;height:36px;flex-shrink:0}
.nav-links{display:flex;align-items:center;gap:32px;list-style:none}
.nav-links a{color:#f5f5f7;font-size:14px;font-weight:400;transition:color .2s}
.nav-links a:hover{color:#fff}

.nav-toggle{display:none;background:none;border:none;cursor:pointer;padding:8px;color:#f5f5f7}
.nav-toggle span{display:block;width:20px;height:2px;background:#f5f5f7;margin:4px 0;transition:.3s}
.nav-toggle.active span:nth-child(1){transform:rotate(45deg) translate(4px,4px)}
.nav-toggle.active span:nth-child(2){opacity:0}
.nav-toggle.active span:nth-child(3){transform:rotate(-45deg) translate(4px,-4px)}

/* --- Hero --- */
.hero{
  min-height:100vh;display:flex;align-items:center;justify-content:center;text-align:center;
  background:#000;color:#fff;position:relative;overflow:hidden;
  padding:80px 0 120px;
}
.hero-bg{
  position:absolute;inset:0;background:radial-gradient(ellipse at 50% 40%,#1a1a2e 0%,#000 70%);
  z-index:0;
}
.hero .container{position:relative;z-index:1}
.hero-title{font-size:clamp(36px,5vw,64px);font-weight:600;line-height:1.1;letter-spacing:-.02em;margin-bottom:16px;max-width:800px;margin-left:auto;margin-right:auto}
.hero-subtitle{font-size:clamp(17px,2vw,24px);font-weight:400;line-height:1.4;color:#a1a1a6;margin-bottom:40px;max-width:600px;margin-left:auto;margin-right:auto}
.hero-cta{display:flex;align-items:center;justify-content:center;gap:28px;flex-wrap:wrap}
.hero-cta a{font-size:19px;font-weight:400;color:#2997ff;transition:color .2s;display:inline-flex;align-items:center;gap:6px}
.hero-cta a:hover{color:#6bbfff}
.hero-cta a::after{content:"›";font-size:22px;line-height:1}

/* --- Features Grid --- */
.features-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:1px;margin-top:64px;background:#d2d2d7}
.section-dark .features-grid{background:#2d2d2f}
.feature-card{background:#fff;padding:48px 40px;transition:background .3s}
.feature-card:hover{background:#f5f5f7}
.section-dark .feature-card{background:#000}
.section-dark .feature-card:hover{background:#1d1d1f}
.feature-card h3{font-size:24px;font-weight:600;margin-bottom:12px;line-height:1.3}
.feature-card p{font-size:17px;color:#86868b;line-height:1.588}
.section-dark .feature-card h3{color:#fff}
.section-dark .feature-card p{color:#a1a1a6}

/* --- Advanced Grid (6 items) --- */
.advanced-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:40px;margin-top:80px}
.advanced-item{text-align:center;padding:0 16px}
.advanced-item h4{font-size:19px;font-weight:600;margin-bottom:8px}
.advanced-item p{font-size:14px;color:#86868b;line-height:1.5}
.section-dark .advanced-item h4{color:#fff}
.section-dark .advanced-item p{color:#a1a1a6}

/* --- Flow Steps --- */
.flow-heading{font-size:28px;font-weight:600;text-align:center;margin-bottom:32px;margin-top:80px}
.section-dark .flow-heading{color:#fff}
.flow-steps{display:flex;justify-content:center;gap:0;margin-top:0;position:relative}
.flow-step{text-align:center;flex:1;max-width:220px;position:relative;padding:0 20px}
.flow-step:not(:last-child)::after{content:"";position:absolute;top:24px;right:-12px;width:24px;height:1px;background:#d2d2d7}
.section-dark .flow-step:not(:last-child)::after{background:#424245}
.flow-step .step-num{width:48px;height:48px;border-radius:50%;background:#0071e3;color:#fff;display:flex;align-items:center;justify-content:center;font-size:17px;font-weight:600;margin:0 auto 16px}
.flow-step .step-title{font-size:17px;font-weight:600;margin-bottom:6px}
.flow-step .step-desc{font-size:13px;color:#86868b;line-height:1.4}
.section-dark .flow-step .step-desc{color:#a1a1a6}

/* --- Cases --- */
.cases-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:32px;margin-top:64px}
.case-card{border:1px solid #d2d2d7;padding:32px 28px;transition:border-color .3s}
.case-card:hover{border-color:#0071e3}
.case-tag{display:inline-block;font-size:12px;font-weight:600;color:#0071e3;text-transform:uppercase;letter-spacing:.05em;margin-bottom:12px}
.case-card h3{font-size:19px;font-weight:600;margin-bottom:8px;line-height:1.4}
.case-result{font-size:14px;color:#0071e3;font-weight:600;margin-bottom:12px}
.case-card p{font-size:14px;color:#86868b;line-height:1.6}
.section-dark .case-card{border-color:#424245}
.section-dark .case-card:hover{border-color:#2997ff}
.section-dark .case-card h3{color:#fff}
.section-dark .case-card p{color:#a1a1a6}
.section-dark .case-result{color:#2997ff}
.section-dark .case-tag{color:#2997ff}

/* --- Comparison Table --- */
.comparison-table{margin-top:64px;overflow-x:auto}
.comparison-table table{width:100%;border-collapse:collapse;font-size:15px}
.comparison-table th{font-size:13px;font-weight:600;color:#86868b;text-align:left;padding:12px 20px;border-bottom:1px solid #d2d2d7}
.section-dark .comparison-table th{color:#a1a1a6;border-color:#424245}
.comparison-table td{padding:16px 20px;border-bottom:1px solid #d2d2d7;line-height:1.5}
.section-dark .comparison-table td{border-color:#424245;color:#f5f5f7}
.comparison-table .col-dim{font-weight:600;color:#1d1d1f}
.section-dark .comparison-table .col-dim{color:#fff}
.comparison-table .col-wb{color:#0071e3;font-weight:500}
.section-dark .comparison-table .col-wb{color:#2997ff}
.comparison-table .col-os{color:#86868b}
.section-dark .comparison-table .col-os{color:#a1a1a6}
.comparison-table tr:last-child td{border-bottom:none}

/* --- Why Us Numbers --- */
.numbers-row{display:flex;justify-content:center;gap:80px;margin-top:64px;flex-wrap:wrap}
.num-item{text-align:center}
.num-value{font-size:64px;font-weight:600;line-height:1;letter-spacing:-.03em;color:#0071e3;margin-bottom:8px}
.section-dark .num-value{color:#2997ff}
.num-label{font-size:17px;color:#86868b}
.section-dark .num-label{color:#a1a1a6}

/* --- Diff Comparison --- */
.diff-block{margin-top:80px}
.diff-table{max-width:700px;margin:0 auto;border-top:1px solid #d2d2d7}
.section-dark .diff-table{border-color:#424245}
.diff-header .diff-left,
.diff-header .diff-right{font-size:17px;font-weight:600;color:#1d1d1f}
.section-dark .diff-header .diff-left,
.section-dark .diff-header .diff-right{color:#fff}
.diff-header{border-bottom:2px solid #d2d2d7}
.diff-header .diff-arrow{color:#86868b;font-size:14px;font-weight:500}
.section-dark .diff-header{border-color:#424245}
.section-dark .diff-header .diff-arrow{color:#86868b}
.diff-row{display:flex;align-items:center;padding:20px 0;border-bottom:1px solid #d2d2d7;gap:20px}
.section-dark .diff-row{border-color:#424245}
.diff-left,.diff-right{flex:1;font-size:15px;line-height:1.5}
.diff-left{color:#86868b}
.diff-right{color:#1d1d1f;font-weight:500}
.section-dark .diff-left{color:#a1a1a6}
.section-dark .diff-right{color:#fff}
.diff-arrow{color:#0071e3;font-size:18px;flex-shrink:0}
.section-dark .diff-arrow{color:#2997ff}

/* --- News Cards --- */
.news-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:32px;margin-top:48px}
.news-card{border:1px solid #d2d2d7;padding:40px 36px;transition:border-color .3s}
.news-card:hover{border-color:#0071e3}
.news-card .news-date{font-size:13px;color:#86868b;letter-spacing:.5px;margin-bottom:16px;text-transform:uppercase}
.news-card h3{font-size:20px;font-weight:600;margin-bottom:10px;line-height:1.35;color:#1d1d1f}
.news-card p{font-size:15px;color:#86868b;line-height:1.75;margin:0}
.news-card .news-link{display:inline-block;margin-top:16px;font-size:14px;font-weight:500;color:#0071e3;text-decoration:none}
.news-empty{text-align:center;padding:60px 0;color:#86868b;font-size:17px}
.news-more-wrap{text-align:center;margin-top:36px}
.news-more-btn{display:inline-block;padding:12px 40px;border:1px solid #0071e3;color:#0071e3;font-size:15px;font-weight:500;cursor:pointer;background:transparent;transition:all .3s}
.news-more-btn:hover{background:#0071e3;color:#fff}

/* --- News Detail Modal --- */
.news-modal{
  position:fixed;inset:0;z-index:9999;
  display:flex;align-items:center;justify-content:center;
  opacity:0;visibility:hidden;transition:opacity .3s,visibility .3s;
}
.news-modal.active{opacity:1;visibility:visible}
.news-modal-backdrop{
  position:absolute;inset:0;background:rgba(0,0,0,.6);
  backdrop-filter:blur(4px);-webkit-backdrop-filter:blur(4px);
}
.news-modal-panel{
  position:relative;z-index:1;
  background:#fff;max-width:760px;width:90vw;max-height:85vh;
  overflow-y:auto;padding:56px 48px 48px;
  transform:translateY(20px);transition:transform .35s ease;
}
.news-modal.active .news-modal-panel{transform:translateY(0)}
.news-modal-close{
  position:absolute;top:16px;right:20px;
  background:none;border:none;font-size:32px;line-height:1;
  color:#86868b;cursor:pointer;padding:4px;transition:color .2s;
}
.news-modal-close:hover{color:#1d1d1f}
.news-modal-date{font-size:13px;color:#86868b;letter-spacing:.5px;margin-bottom:12px;text-transform:uppercase}
.news-modal-title{font-size:32px;font-weight:600;line-height:1.25;letter-spacing:-.01em;color:#1d1d1f;margin-bottom:32px}
.news-modal-body{font-size:17px;line-height:1.85;color:#1d1d1f;white-space:pre-wrap}
.news-modal-body p{margin-bottom:1em}

@media(max-width:767px){
  .news-modal-panel{padding:40px 24px 36px;width:94vw;max-height:90vh}
  .news-modal-title{font-size:24px;margin-bottom:24px}
  .news-modal-body{font-size:16px;line-height:1.75}
  .news-modal-close{top:12px;right:12px;font-size:28px}
}

/* --- Timeline --- */
.timeline{position:relative;margin-top:48px;padding-left:40px}
.timeline::before{content:"";position:absolute;left:12px;top:0;bottom:0;width:1px;background:#d2d2d7}
.section-dark .timeline::before{background:#424245}
.timeline-item{position:relative;padding-bottom:40px}
.timeline-item:last-child{padding-bottom:0}
.timeline-item::before{content:"";position:absolute;left:-32px;top:6px;width:9px;height:9px;border-radius:50%;background:#0071e3}
.timeline-year{font-size:14px;font-weight:600;color:#0071e3;margin-bottom:4px}
.section-dark .timeline-year{color:#2997ff}
.timeline-event{font-size:19px;font-weight:400;line-height:1.5}
.section-dark .timeline-event{color:#f5f5f7}

/* --- Mission Block --- */
.mission-block{margin-top:80px;max-width:860px}
.mission-block h3{font-size:28px;font-weight:600;margin-bottom:20px}
.mission-block p{font-size:17px;line-height:1.8;color:#86868b;margin-bottom:16px}
.mission-block p:last-child{margin-bottom:0}
.section-dark .mission-block p{color:#a1a1a6}

/* --- Team Grid --- */
.team-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:40px;margin-top:64px}
.team-card{text-align:center;padding:0 16px}
.team-photo{width:160px;height:160px;border-radius:50%;margin:0 auto 24px;background:#f5f5f7;overflow:hidden;display:flex;align-items:center;justify-content:center;color:#86868b;font-size:14px}
.section-dark .team-photo{background:#1d1d1f;color:#86868b}
.team-photo img{width:100%;height:100%;object-fit:cover}
.team-name{font-size:24px;font-weight:600;margin-bottom:6px}
.team-role{font-size:14px;color:#0071e3;font-weight:500;margin-bottom:12px}
.section-dark .team-role{color:#2997ff}
.team-desc{font-size:14px;color:#86868b;line-height:1.6;max-width:280px;margin:0 auto}
.section-dark .team-desc{color:#a1a1a6}

/* --- Contact --- */
.contact-block{margin-top:48px;display:flex;justify-content:center;align-items:flex-start;gap:64px;flex-wrap:wrap}
.qr-card{text-align:center}
.qr-card img{width:180px;height:180px;border:1px solid #d2d2d7;margin-bottom:16px}
.section-dark .qr-card img{border-color:#424245}
.qr-card span{font-size:14px;color:#86868b;display:block}
.section-dark .qr-card span{color:#a1a1a6}
.contact-cta{margin-top:40px;text-align:center}
.contact-cta .btn{display:inline-block;font-size:19px;color:#0071e3;font-weight:500}
.contact-cta .btn::after{content:" ›";font-size:20px}
.section-dark .contact-cta .btn{color:#2997ff}

/* --- Footer --- */
.footer{background:#1d1d1f;padding:64px 0 0;color:#a1a1a6;font-size:13px}
.footer-grid{display:grid;grid-template-columns:2fr 1fr 1fr 1fr;gap:48px;padding-bottom:48px;border-bottom:1px solid #424245}
.footer-logo{display:flex;align-items:center;gap:10px;margin-bottom:16px}
.footer-logo-img{height:28px;width:auto}
.footer-logo span{font-size:17px;font-weight:600;color:#f5f5f7}
.footer-tagline{color:#a1a1a6;line-height:1.8;font-size:13px;max-width:320px}
.footer-col-title{font-size:13px;font-weight:600;color:#f5f5f7;margin-bottom:16px;letter-spacing:.5px}
.footer-links{list-style:none;padding:0;margin:0}
.footer-links li{margin-bottom:10px;color:#a1a1a6}
.footer-links a{color:#a1a1a6;text-decoration:none;transition:color .2s}
.footer-links a:hover{color:#f5f5f7}
.footer-bottom{padding:24px 0 32px;text-align:center}
.footer-bottom p{color:#a1a1a6;font-size:13px}
.footer-bottom a{color:#a1a1a6;text-decoration:none}
.footer-bottom a:hover{color:#f5f5f7}

/* --- Scroll Animations --- */
.reveal{opacity:0;transform:translateY(30px);transition:opacity .8s ease,transform .8s ease}
.reveal.visible{opacity:1;transform:translateY(0)}

/* --- Responsive: Tablet --- */
@media(max-width:1024px){
  .container{padding:0 32px}
  .section{padding:80px 0}
  .section-title{font-size:36px}
  .section-subtitle{font-size:18px}
  .features-grid{grid-template-columns:1fr 1fr}
  .cases-grid{grid-template-columns:1fr 1fr}
  .news-grid{grid-template-columns:1fr 1fr}
  .team-grid{grid-template-columns:repeat(3,1fr);gap:24px}
  .flow-steps{flex-wrap:wrap;gap:32px;justify-content:center}
  .flow-step{max-width:180px}
  .flow-step:not(:last-child)::after{display:none}
  .numbers-row{gap:40px}
  .num-value{font-size:48px}
  .footer-grid{grid-template-columns:1fr 1fr;gap:36px}
}

/* --- Responsive: Mobile --- */
@media(max-width:767px){
  .container{padding:0 20px}
  .section{padding:64px 0}
  .section-title{font-size:28px}
  .section-subtitle{font-size:16px}
  .hero{min-height:100vh;padding:80px 0 100px}
  .hero-title{font-size:28px}
  .hero-subtitle{font-size:16px;margin-bottom:28px}
  .hero-cta{gap:20px}
  .hero-cta a{font-size:16px}

  /* Mobile Nav */
  .nav-links{display:none;position:fixed;top:56px;left:0;right:0;background:rgba(29,29,31,.95);flex-direction:column;padding:24px 20px;gap:16px;backdrop-filter:blur(20px)}
  .nav-links.open{display:flex}
  .nav-toggle{display:block;position:relative;z-index:1001}

  .features-grid{grid-template-columns:1fr}
  .feature-card{padding:32px 24px}
  .advanced-grid{grid-template-columns:1fr 1fr;gap:24px}
  .cases-grid{grid-template-columns:1fr;gap:16px}
  .news-grid{grid-template-columns:1fr;gap:16px}
  .team-grid{grid-template-columns:1fr;gap:32px}
  .flow-steps{flex-direction:column;align-items:center;gap:24px}
  .flow-step{max-width:100%}
  .numbers-row{gap:28px}
  .num-value{font-size:36px}
  .num-label{font-size:14px}
  .comparison-table{font-size:13px}
  .comparison-table th,.comparison-table td{padding:10px 12px}
  .contact-block{gap:32px}
  .qr-card img{width:140px;height:140px}
  .timeline{padding-left:28px}
  .timeline-item::before{left:-24px}
  .diff-table{border:none}
  .diff-row{flex-direction:column;align-items:stretch;gap:0;padding:16px 0;border-bottom:1px solid #d2d2d7}
  .diff-header{flex-direction:row;gap:8px;padding:16px 0;border-bottom:2px solid #d2d2d7}
  .diff-header .diff-left,.diff-header .diff-right{font-size:14px;font-weight:600;flex:1;text-align:center}
  .diff-header .diff-arrow{display:flex;align-items:center;justify-content:center;font-size:14px;flex-shrink:0}
  .diff-left,.diff-right{flex:none;font-size:14px;padding:10px 16px;border-radius:0;line-height:1.6}
  .diff-left{background:rgba(134,134,139,.08);margin-bottom:6px;position:relative}
  .diff-left::before{content:"❌ ";font-size:13px}
  .diff-right{background:rgba(0,113,227,.06);position:relative}
  .diff-right::before{content:"✅ ";font-size:13px}
  .diff-arrow{display:none}
  .section-dark .diff-row{border-color:#424245}
  .section-dark .diff-left{background:rgba(255,255,255,.04)}
  .section-dark .diff-right{background:rgba(41,151,255,.08)}
  .footer-grid{grid-template-columns:1fr;gap:24px}
  .footer-hide-mobile{display:none}
  .footer-brand{text-align:center;display:flex;flex-direction:column;align-items:center}
  .footer-logo{justify-content:center}
  .footer-tagline{max-width:100%;text-align:center}
}

/* --- Print --- */
@media print{
  .navbar,.nav-toggle{display:none}
  .section{padding:40px 0;break-inside:avoid}
  .hero{min-height:auto;padding:40px 0}
}