/* ===== 基础重置 ===== */
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth;font-size:16px}
body{
  font-family:'Microsoft YaHei','PingFang SC','Helvetica Neue',Helvetica,Arial,sans-serif;
  color:#1a2a3a;
  background:#f0f5fb;
  overflow-x:hidden;
  line-height:1.7;
}

/* ===== 滚动条 ===== */
::-webkit-scrollbar{width:5px}
::-webkit-scrollbar-track{background:#eaf2ff}
::-webkit-scrollbar-thumb{background:#a0c8e8;border-radius:3px}
::-webkit-scrollbar-thumb:hover{background:#0077ff}

/* ===== 导航栏 ===== */
#navbar{
  position:fixed;top:0;left:0;right:0;z-index:1200;
  padding:0 48px;
  height:68px;
  display:flex;align-items:center;justify-content:space-between;
  background:rgba(235,245,255,0.95);
  border-bottom:1px solid rgba(0,120,220,0.12);
  backdrop-filter:blur(18px);
  transition:background .3s,box-shadow .3s;
}
#navbar.scrolled{
  background:rgba(235,245,255,0.99);
  border-bottom-color:rgba(0,120,220,0.18);
  box-shadow:0 2px 24px rgba(0,100,200,0.1);
}
.nav-logo{display:flex;align-items:center;gap:12px;text-decoration:none}
.logo-icon{
  width:36px;height:36px;
  background:linear-gradient(135deg,#0077ff,#00aaff);
  border-radius:8px;
  display:flex;align-items:center;justify-content:center;
  font-weight:900;font-size:16px;color:#fff;letter-spacing:-1px;
}
.logo-text{font-size:17px;font-weight:700;color:#1a3a5c;letter-spacing:1.5px;line-height:1.2}
.logo-sub{font-size:10px;color:#5a8ab0;letter-spacing:3px;font-weight:400;text-transform:uppercase}
.nav-links-pc{display:flex;align-items:center;gap:4px}
.nav-links-pc a{
  color:#5a7a96;text-decoration:none;
  padding:6px 16px;font-size:14px;
  border-radius:6px;transition:all .25s;letter-spacing:.5px;
}
.nav-links-pc a:hover,.nav-links-pc a.active{color:#0066dd;background:rgba(0,102,221,0.07)}
.nav-links-mobile{display:none}
.nav-links-mobile.open{
  display:flex;position:fixed;top:0;left:0;right:0;bottom:0;
  background:rgba(240,245,255,1);
  flex-direction:column;align-items:center;justify-content:center;gap:8px;
  z-index:1102;
}
.nav-links-mobile a{
  font-size:17px;padding:10px 40px;color:#1a2a3a;
  width:80%;text-align:center;border-radius:10px;
  text-decoration:none;
}
.nav-links-mobile a.active{color:#0077ff;background:rgba(0,119,255,.08)}
.nav-links-mobile a:hover{color:#0077ff;background:rgba(0,119,255,.08)}
.nav-cta{border:1px solid rgba(0,102,221,.4)!important;color:#0066dd!important;margin-left:8px}
.nav-cta:hover{background:rgba(0,102,221,.08)!important;border-color:#0066dd!important;color:#0052bb!important}
.menu-btn{
  display:none;align-items:center;gap:6px;
  padding:6px 14px;
  background:#fff;
  border:1px solid rgba(0,102,221,.2);
  border-radius:8px;
  color:#0066dd;
  font-size:14px;font-weight:600;
  cursor:pointer;transition:all .2s;
  position:relative;z-index:1101;
}
.menu-btn:hover{background:#0066dd;color:#fff;border-color:#0066dd}

/* ===== 背景画布 ===== */
#bgCanvas{position:fixed;top:0;left:0;width:100%;height:100%;z-index:0;pointer-events:none}

/* ===== 主内容 ===== */
main{position:relative;z-index:1}

/* ===== 各 section 通用 ===== */
section{min-height:100vh;padding:120px 0 80px}
.section-tag{
  display:inline-flex;align-items:center;gap:8px;
  font-size:11px;letter-spacing:4px;text-transform:uppercase;
  color:#0066dd;margin-bottom:20px;font-weight:600;
}
.section-tag::before{content:'';width:28px;height:2px;background:#0066dd}
.section-title{font-size:clamp(28px,4vw,48px);font-weight:800;color:#1a2a3a;line-height:1.2;margin-bottom:18px;letter-spacing:-.5px}
.section-desc{font-size:16px;color:#5a7a96;max-width:580px;line-height:1.9}

/* ===== 按钮样式 ===== */
.btn-primary{
  display:inline-flex;align-items:center;gap:10px;
  padding:13px 32px;background:linear-gradient(135deg,#0066dd,#0090ff);
  color:#fff;border:none;border-radius:8px;
  font-size:15px;font-weight:600;cursor:pointer;text-decoration:none;letter-spacing:.5px;
  transition:all .3s;position:relative;overflow:hidden;
  box-shadow:0 4px 20px rgba(0,102,221,.25);
}
.btn-primary::before{
  content:'';position:absolute;top:0;left:-100%;width:100%;height:100%;
  background:linear-gradient(90deg,transparent,rgba(255,255,255,.2),transparent);
  transition:left .5s;
}
.btn-primary:hover::before{left:100%}
.btn-primary:hover{transform:translateY(-2px);box-shadow:0 8px 28px rgba(0,102,221,.4)}
.btn-outline{
  display:inline-flex;align-items:center;gap:10px;padding:12px 30px;
  border:1px solid rgba(0,102,221,.4);color:#0066dd;border-radius:8px;
  font-size:15px;font-weight:600;cursor:pointer;text-decoration:none;letter-spacing:.5px;
  transition:all .3s;background:transparent;
}
.btn-outline:hover{border-color:#0066dd;background:rgba(0,102,221,.06);color:#0052bb;transform:translateY(-2px)}

/* ===== =========== ===== */
/* ===== 首页 HERO  ===== */
/* ===== =========== ===== */
#home{min-height:100vh;display:flex;align-items:center;padding:0;position:relative;overflow:hidden}
.hero-inner{max-width:1200px;margin:0 auto;padding:0 60px;width:100%}
.hero-badge{
  display:inline-flex;align-items:center;gap:8px;
  padding:6px 18px;border:1px solid rgba(0,102,221,.25);
  border-radius:50px;font-size:12px;color:#0066dd;background:rgba(0,102,221,.05);
  letter-spacing:1px;margin-bottom:36px;
}
.hero-badge-dot{width:6px;height:6px;border-radius:50%;background:#0066dd;animation:pulse-dot 2s infinite}
@keyframes pulse-dot{0%,100%{opacity:1;transform:scale(1)}50%{opacity:.5;transform:scale(.6)}}
.hero-title{font-size:clamp(38px,6vw,72px);font-weight:900;color:#1a2a3a;line-height:1.1;margin-bottom:24px;letter-spacing:-1px}
.hero-title .accent{color:#0066dd}
.hero-title .glow{color:#0090ff}
.hero-sub{font-size:clamp(15px,2vw,19px);color:#5a7a96;max-width:560px;line-height:2;margin-bottom:48px}
.hero-actions{display:flex;gap:16px;flex-wrap:wrap}
.hero-stats{display:flex;gap:60px;margin-top:80px;padding-top:48px;border-top:1px solid rgba(0,102,221,.1)}
.stat-item{}
.stat-num{
  font-size:42px;font-weight:900;
  background:linear-gradient(135deg,#0066dd,#0090ff);
  -webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text;
  line-height:1;margin-bottom:8px;
}
.stat-label{font-size:13px;color:#5a7a96;letter-spacing:1px}

/* 装饰圆形 */
.hero-circle{position:absolute;border-radius:50%;border:1px solid rgba(0,120,220,.1);pointer-events:none}
.hero-circle-1{width:600px;height:600px;right:-200px;top:50%;transform:translateY(-50%)}
.hero-circle-2{width:400px;height:400px;right:-100px;top:50%;transform:translateY(-50%)}
.hero-circle-3{width:200px;height:200px;right:50px;top:50%;transform:translateY(-50%);border-color:rgba(0,120,220,.2)}
.hero-grid{position:absolute;right:60px;top:50%;transform:translateY(-50%);width:320px;display:grid;grid-template-columns:1fr 1fr;gap:2px;opacity:.1}
.hero-grid-cell{aspect-ratio:1;background:rgba(0,102,221,.5);border-radius:4px}

/* ===== =========== ===== */
/* ===== 关于我们      ===== */
/* ===== =========== ===== */
#about{padding-top:120px}
.about-grid{max-width:1200px;margin:0 auto;padding:0 60px;display:grid;grid-template-columns:1fr 1fr;gap:80px;align-items:center}
.about-visual{position:relative;height:500px}
.about-card{
  position:absolute;background:rgba(255,255,255,.95);border:1px solid rgba(0,102,221,.12);
  border-radius:16px;padding:28px;backdrop-filter:blur(10px);
  box-shadow:0 4px 24px rgba(0,60,140,.08);transition:transform .3s,box-shadow .3s;
}
.about-card:hover{transform:translateY(-4px);box-shadow:0 12px 36px rgba(0,102,221,.12)}
.about-card-active{transform:translateY(-6px) scale(1.03);box-shadow:0 16px 48px rgba(0,102,221,.18)!important;border-color:rgba(0,120,220,.3)!important}
.about-card-1{top:0;left:0;width:260px}
.about-card-2{top:120px;right:0;width:240px}
.about-card-3{bottom:40px;left:40px;width:280px}
.card-icon{
  width:48px;height:48px;border-radius:12px;
  background:linear-gradient(135deg,rgba(0,102,221,.1),rgba(0,144,255,.08));
  border:1px solid rgba(0,102,221,.2);
  display:flex;align-items:center;justify-content:center;margin-bottom:16px;font-size:22px;
}
.card-title{font-size:16px;font-weight:700;color:#1a2a3a;margin-bottom:8px}
.card-text{font-size:13px;color:#5a7a96;line-height:1.7}
.about-text-wrap .section-desc{margin-bottom:36px}
.about-values{display:grid;grid-template-columns:1fr 1fr;gap:20px}
.value-item{padding:20px;background:#fff;border:1px solid rgba(0,102,221,.1);border-radius:12px;transition:border-color .3s,box-shadow .3s}
.value-item:hover{border-color:rgba(0,102,221,.25);box-shadow:0 4px 16px rgba(0,60,140,.06)}
.value-item h4{font-size:15px;font-weight:700;color:#1a2a3a;margin-bottom:8px}
.value-item p{font-size:13px;color:#5a7a96;line-height:1.7}

/* ===== =========== ===== */
/* ===== 产品服务      ===== */
/* ===== =========== ===== */
#services{padding-top:120px;background:linear-gradient(180deg,#f0f5fb,rgba(230,240,250,.5),#f0f5fb)}
.services-header{max-width:1200px;margin:0 auto 60px;padding:0 60px;display:flex;align-items:flex-end;justify-content:space-between}
.services-header .section-desc{max-width:420px;text-align:right}
.services-grid{max-width:1200px;margin:0 auto;padding:0 60px;display:grid;grid-template-columns:repeat(3,1fr);gap:24px}
.service-card{
  background:#fff;border:1px solid rgba(0,102,221,.1);border-radius:16px;padding:36px 28px;
  position:relative;overflow:hidden;transition:all .35s;cursor:default;
}
.service-card::before{content:'';position:absolute;top:0;left:0;right:0;height:2px;background:linear-gradient(90deg,transparent,#0066dd,#0090ff,transparent);opacity:0;transition:opacity .35s}
.service-card:hover{border-color:rgba(0,102,221,.3);transform:translateY(-6px);box-shadow:0 16px 48px rgba(0,60,140,.1)}
.service-card:hover::before{opacity:1}
.service-icon{width:56px;height:56px;border-radius:14px;background:linear-gradient(135deg,rgba(0,102,221,.1),rgba(0,144,255,.08));border:1px solid rgba(0,102,221,.15);display:flex;align-items:center;justify-content:center;font-size:26px;margin-bottom:24px}
.service-card h3{font-size:19px;font-weight:700;color:#1a2a3a;margin-bottom:14px}
.service-card p{font-size:14px;color:#5a7a96;line-height:1.85;margin-bottom:20px}
.service-tags{display:flex;flex-wrap:wrap;gap:8px}
.service-tag{padding:4px 12px;font-size:11px;border:1px solid rgba(0,102,221,.2);border-radius:4px;color:#0066dd;background:rgba(0,102,221,.04);letter-spacing:.5px}
.service-number{position:absolute;top:24px;right:24px;font-size:64px;font-weight:900;color:rgba(0,102,221,.04);line-height:1;pointer-events:none;transition:color .3s}
.service-card:hover .service-number{color:rgba(0,102,221,.08)}
.features-strip{max-width:1200px;margin:60px auto 0;padding:40px 60px;background:linear-gradient(135deg,rgba(0,102,221,.06),rgba(0,144,255,.03));border:1px solid rgba(0,102,221,.12);border-radius:20px;display:grid;grid-template-columns:repeat(4,1fr);gap:40px}
.feature-item{text-align:center}
.feature-item .f-icon{font-size:28px;margin-bottom:12px;display:block}
.feature-item h4{font-size:15px;font-weight:700;color:#1a2a3a;margin-bottom:6px}
.feature-item p{font-size:13px;color:#5a7a96}

/* ===== =========== ===== */
/* ===== 联系我们      ===== */
/* ===== =========== ===== */
#contact{padding-top:120px}
.contact-grid{max-width:1200px;margin:0 auto;padding:0 60px;display:grid;grid-template-columns:1fr 1fr;gap:60px}
.contact-info .section-desc{margin-bottom:40px}
.contact-list{list-style:none;display:flex;flex-direction:column;gap:24px}
.contact-item{display:flex;align-items:flex-start;gap:16px;cursor:pointer;transition:opacity .2s}
.contact-item:hover .contact-item-text strong{color:#0077ff}
.contact-item-icon{width:44px;height:44px;flex-shrink:0;border-radius:10px;background:rgba(0,102,221,.07);border:1px solid rgba(0,102,221,.15);display:flex;align-items:center;justify-content:center;font-size:20px}
.contact-item-text strong{display:block;font-size:15px;color:#1a2a3a;margin-bottom:4px}
.contact-item-text span{font-size:14px;color:#5a7a96}
.contact-form{background:#fff;border:1px solid rgba(0,102,221,.1);border-radius:20px;padding:44px;box-shadow:0 4px 24px rgba(0,60,140,.06)}
.form-row{display:grid;grid-template-columns:1fr 1fr;gap:20px;margin-bottom:20px}
.form-group{margin-bottom:20px}
.form-group:last-of-type{margin-bottom:0}
.form-group label{display:block;font-size:13px;color:#5a7a96;margin-bottom:8px;letter-spacing:.5px;font-weight:500}
.form-group input,.form-group textarea{width:100%;background:#f8fafd;border:1px solid rgba(0,102,221,.15);border-radius:8px;padding:12px 16px;color:#1a2a3a;font-size:14px;font-family:inherit;transition:border-color .25s,box-shadow .25s;outline:none}
.form-group input::placeholder,.form-group textarea::placeholder{color:#a0b8d0}
.form-group input:focus,.form-group textarea:focus{border-color:#0066dd;box-shadow:0 0 0 3px rgba(0,102,221,.08)}
.form-group textarea{resize:vertical;min-height:120px}
.form-submit{width:100%;margin-top:24px;padding:14px;font-size:15px;box-shadow:0 4px 20px rgba(0,102,221,.2)}
.form-success{display:none;text-align:center;padding:40px 20px}
.form-success.show{display:block}
.form-success .success-icon{font-size:48px;margin-bottom:16px}
.form-success h3{font-size:22px;color:#1a2a3a;margin-bottom:10px}
.form-success p{font-size:14px;color:#5a7a96}

/* ===== =========== ===== */
/* ===== 页脚          ===== */
/* ===== =========== ===== */
footer{border-top:1px solid rgba(0,120,220,.08);padding:48px 0 32px;position:relative;z-index:1;background:#eaf4ff}
.footer-inner{max-width:1200px;margin:0 auto;padding:0 60px;display:grid;grid-template-columns:2fr 1fr 1fr 1fr;gap:40px}
.footer-logo{display:flex;align-items:center;gap:12px;margin-bottom:16px;text-decoration:none}
.footer-brand p{font-size:13px;color:#5a7a96;line-height:1.8;max-width:280px}
.footer-col h4{font-size:13px;font-weight:700;color:#5a7a96;letter-spacing:2px;text-transform:uppercase;margin-bottom:20px}
.footer-col ul{list-style:none;display:flex;flex-direction:column;gap:10px}
.footer-col ul a{font-size:13px;color:#5a7a96;text-decoration:none;transition:color .2s}
.footer-col ul a:hover{color:#0066dd}
.footer-bottom{max-width:1200px;margin:40px auto 0;padding:20px 60px 0;border-top:1px solid rgba(0,102,221,.06);display:flex;align-items:center;justify-content:space-between;flex-wrap:wrap;gap:10px}
.footer-bottom-left p{font-size:12px;color:#8aacc8}
.footer-bottom p:last-child{font-size:12px;color:#8aacc8}
.footer-bottom a{color:#8aacc8;text-decoration:none}
.footer-bottom a:hover{color:#0066dd}

/* ===== 二维码弹窗 ===== */
.qr-popup{position:fixed;top:0;left:0;right:0;bottom:0;z-index:10000;display:flex;align-items:center;justify-content:center}
.qr-popup-mask{position:absolute;inset:0;background:rgba(0,0,0,.5);backdrop-filter:blur(4px)}
.qr-popup-box{position:relative;background:#fff;border-radius:20px;padding:40px 36px;max-width:360px;width:90%;text-align:center;box-shadow:0 20px 60px rgba(0,0,0,.2);animation:qrPopIn .3s ease}
@keyframes qrPopIn{from{opacity:0;transform:scale(.9)}to{opacity:1;transform:scale(1)}}
.qr-popup-close{position:absolute;top:16px;right:18px;background:none;border:none;font-size:20px;color:#a0b8d0;cursor:pointer;padding:4px;line-height:1;transition:color .2s}
.qr-popup-close:hover{color:#1a2a3a}
.qr-popup-title{font-size:20px;font-weight:800;color:#1a2a3a;margin-bottom:10px}
.qr-popup-desc{font-size:13px;color:#5a7a96;line-height:1.7;margin-bottom:24px}
.qr-popup-img{width:200px;height:200px;margin:0 auto;border-radius:12px;overflow:hidden;border:1px solid rgba(0,102,221,.15)}
.qr-placeholder{width:100%;height:100%;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:8px;background:#f8fafd}
.qr-placeholder p{font-size:13px;color:#5a7a96;font-weight:600}
.qr-placeholder small{font-size:11px;color:#a0b8d0}

/* ===== =========== ===== */
/* ===== 动画          ===== */
/* ===== =========== ===== */
.reveal{opacity:0;transform:translateY(30px);transition:opacity .7s ease,transform .7s ease}
.reveal.visible{opacity:1;transform:translateY(0)}
.reveal-delay-1{transition-delay:.1s}
.reveal-delay-2{transition-delay:.2s}
.reveal-delay-3{transition-delay:.3s}
.reveal-delay-4{transition-delay:.4s}
.reveal-delay-5{transition-delay:.5s}

/* ===== =========== ===== */
/* ===== 移动端        ===== */
/* ===== =========== ===== */
@media(max-width:900px){
  #navbar{padding:0 16px;height:56px}
  .logo-icon{width:30px!important;height:30px!important;font-size:13px!important}
  .logo-text{font-size:15px!important}
  .logo-sub{font-size:9px!important;letter-spacing:2px!important}
  .nav-links-pc{display:none!important}
  .menu-btn{display:inline-flex}
  .nav-links-mobile{display:none}
  .nav-links-mobile.open{display:flex;position:fixed;top:0;left:0;right:0;bottom:0;background:rgba(240,245,255,1);flex-direction:column;align-items:center;justify-content:center;gap:8px;z-index:1102}
  .nav-links-mobile a{font-size:17px;padding:10px 40px;color:#1a2a3a;width:80%;text-align:center;border-radius:10px;text-decoration:none}
  .nav-links-mobile a.active{color:#0077ff;background:rgba(0,119,255,.08)}
  .nav-links-mobile a:hover{color:#0077ff;background:rgba(0,119,255,.08)}
  .nav-cta{border:1px solid rgba(0,119,255,.3)!important;color:#0077ff!important;margin-left:0!important;margin-top:12px}

  .hero-inner{padding:0 20px}
  .hero-badge{font-size:11px!important;padding:5px 14px!important}
  .hero-title{font-size:32px!important;margin-bottom:16px!important}
  .hero-sub{font-size:14px!important;margin-bottom:32px!important}
  .hero-actions{flex-direction:column;gap:12px}
  .hero-actions a{width:100%;text-align:center;justify-content:center}
  .hero-grid,.hero-circle{display:none}
  .hero-stats{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin-top:40px;padding-top:32px}
  .stat-item{background:#fff;border:1px solid rgba(0,102,221,.1);border-radius:14px;padding:20px 16px;text-align:center;box-shadow:0 2px 12px rgba(0,60,140,.06)}
  .stat-num{font-size:34px!important;margin-bottom:6px}
  .stat-label{font-size:11px!important;line-height:1.5}

  .about-grid{grid-template-columns:1fr;padding:0 20px;gap:32px}
  .about-visual{height:auto;position:static;display:flex;flex-direction:column;gap:14px}
  .about-card{position:static!important;width:100%!important;transform:none!important;box-shadow:0 2px 16px rgba(0,60,140,.06);border-radius:14px}
  .about-card-active{transform:none!important;box-shadow:0 6px 28px rgba(0,102,221,.14)!important;border-color:rgba(0,120,220,.3)!important}
  .about-values{grid-template-columns:1fr;gap:12px}
  .value-item{padding:16px;border-radius:12px}
  .value-item h4{font-size:14px}
  .value-item p{font-size:13px}

  .services-header{padding:0 20px;gap:12px}
  .services-grid{grid-template-columns:1fr;padding:0 20px;gap:16px}
  .service-card{padding:28px 20px;border-radius:14px}
  .service-card h3{font-size:17px}
  .service-card p{font-size:13px}
  .service-number{font-size:48px!important;top:16px!important;right:16px!important}
  .features-strip{grid-template-columns:1fr;padding:20px 20px;gap:0;border-radius:14px}
  .feature-item{display:flex;align-items:center;gap:14px;padding:14px 0;border-bottom:1px solid rgba(0,102,221,.08);text-align:left}
  .feature-item:last-child{border-bottom:none}
  .feature-item .f-icon{margin-bottom:0;font-size:22px;flex-shrink:0;min-width:24px}
  .feature-item h4{font-size:14px;margin-bottom:2px;flex:1;text-align:justify}
  .feature-item p{font-size:12px;color:#5a7a96;flex:2;text-align:justify;line-height:1.6}

  .contact-grid{grid-template-columns:1fr;padding:0 20px;gap:36px}
  .contact-form{padding:28px 20px;border-radius:16px}
  .form-group{margin-bottom:16px}
  .form-row{grid-template-columns:1fr;gap:0}
  .qr-popup-box{padding:32px 24px;max-width:320px}
  .qr-popup-img{width:180px;height:180px}

  .footer-inner{grid-template-columns:1fr 1fr;gap:0;padding:0 20px}
  .footer-brand{grid-column:1 / -1;margin-bottom:4px}
  .footer-col:nth-child(4){grid-column:1 / -1;padding-top:20px;border-top:1px solid rgba(0,102,221,.1);margin-top:4px}
  .footer-brand p{max-width:100%;margin-bottom:0}
  .footer-col ul{gap:8px}
  .footer-col ul li{display:flex;align-items:center;gap:6px}
  .footer-bottom{flex-direction:column;gap:8px;text-align:center;padding:16px 20px 0}
  .footer-bottom-left{text-align:center;width:100%}
  .footer-col h4{font-size:14px;border-top:none;padding-top:0;margin-bottom:14px;text-align:left}
  .footer-col ul a{justify-content:space-between;display:flex;width:100%;text-align:justify}

  section{padding:72px 0 60px}
}
/* ===== 返回顶部按钮 ===== */
.back-to-top{
  position:fixed;
  right:32px;
  bottom:32px;
  width:44px;
  height:44px;
  background:rgba(0,102,221,.9);
  color:#fff;
  border:none;
  border-radius:10px;
  cursor:pointer;
  display:none;
  align-items:center;
  justify-content:center;
  font-size:18px;
  box-shadow:0 4px 16px rgba(0,102,221,.3);
  transition:opacity .25s,transform .25s,background .2s;
  z-index:900;
  line-height:1;
}
.back-to-top:hover{background:rgba(0,70,180,.95);transform:translateY(-2px)}
.back-to-top.visible{display:flex}
@media(max-width:600px){
  .back-to-top{right:20px;bottom:20px;width:40px;height:40px}
}