/* ============================================
   51视频 - 原创CSS样式表
   品牌色: 珊瑚红 #FF4757 / 深海蓝 #1E3A5F / 星空紫 #6C5CE7
   ============================================ */

/* CSS Reset & Base */
*,*::before,*::after{margin:0;padding:0;box-sizing:border-box}
html{font-size:16px;scroll-behavior:smooth}
body{font-family:"PingFang SC","Hiragino Sans GB","Microsoft YaHei","WenQuanYi Micro Hei",sans-serif;color:#2d3436;background:#f8f9fa;line-height:1.7;overflow-x:hidden}
a{color:#FF4757;text-decoration:none;transition:color .3s}
a:hover{color:#6C5CE7}
img{max-width:100%;height:auto;display:block}
ul,ol{list-style:none}
h1,h2,h3,h4,h5,h6{font-weight:700;line-height:1.3;color:#1E3A5F}

/* Container */
.container{max-width:1200px;margin:0 auto;padding:0 20px}

/* ============ Header ============ */
.site-header{background:linear-gradient(135deg,#1E3A5F 0%,#2C3E6B 100%);position:sticky;top:0;z-index:1000;box-shadow:0 2px 20px rgba(0,0,0,.15)}
.header-inner{display:flex;align-items:center;justify-content:space-between;padding:12px 20px;max-width:1200px;margin:0 auto}
.logo-wrap{display:flex;align-items:center;gap:10px}
.logo-wrap img{height:42px;width:auto}
.logo-text{color:#fff;font-size:1.4rem;font-weight:800;letter-spacing:1px}
.logo-text span{color:#FF4757}

/* Navigation */
.main-nav{display:flex;align-items:center;gap:0}
.main-nav a{color:rgba(255,255,255,.88);padding:10px 16px;font-size:.95rem;font-weight:500;border-radius:6px;transition:all .3s}
.main-nav a:hover,.main-nav a.active{color:#fff;background:rgba(255,71,87,.25)}
.mobile-toggle{display:none;background:none;border:none;color:#fff;font-size:1.6rem;cursor:pointer;padding:8px}

/* Search Bar */
.search-bar{background:linear-gradient(90deg,#FF4757 0%,#6C5CE7 100%);padding:14px 0}
.search-wrap{max-width:680px;margin:0 auto;display:flex;gap:0;padding:0 20px}
.search-wrap input{flex:1;padding:12px 20px;border:none;border-radius:25px 0 0 25px;font-size:1rem;outline:none;background:#fff}
.search-wrap button{padding:12px 28px;background:#1E3A5F;color:#fff;border:none;border-radius:0 25px 25px 0;font-size:1rem;cursor:pointer;font-weight:600;transition:background .3s}
.search-wrap button:hover{background:#FF4757}

/* ============ Hero Banner ============ */
.hero-section{position:relative;overflow:hidden;min-height:420px;display:flex;align-items:center;background:#1E3A5F}
.hero-bg{position:absolute;inset:0;background-size:cover;background-position:center;opacity:.55}
.hero-content{position:relative;z-index:2;text-align:center;width:100%;padding:60px 20px}
.hero-content h1{color:#fff;font-size:2.6rem;margin-bottom:16px;text-shadow:0 2px 12px rgba(0,0,0,.4)}
.hero-content h1 span{color:#FF4757}
.hero-content p{color:rgba(255,255,255,.9);font-size:1.15rem;max-width:700px;margin:0 auto 28px}
.hero-btns{display:flex;gap:16px;justify-content:center;flex-wrap:wrap}
.btn-primary{display:inline-block;padding:14px 36px;background:linear-gradient(135deg,#FF4757,#e84118);color:#fff;border-radius:30px;font-weight:700;font-size:1.05rem;transition:transform .3s,box-shadow .3s;border:none;cursor:pointer}
.btn-primary:hover{transform:translateY(-2px);box-shadow:0 8px 25px rgba(255,71,87,.4);color:#fff}
.btn-secondary{display:inline-block;padding:14px 36px;background:transparent;color:#fff;border:2px solid rgba(255,255,255,.6);border-radius:30px;font-weight:700;font-size:1.05rem;transition:all .3s}
.btn-secondary:hover{background:rgba(255,255,255,.15);border-color:#fff;color:#fff}

/* ============ Section Common ============ */
.section{padding:60px 0}
.section-dark{background:#1E3A5F;color:#fff}
.section-dark h2,.section-dark h3,.section-dark h4{color:#fff}
.section-alt{background:#eef1f5}
.section-title{text-align:center;margin-bottom:45px}
.section-title h2{font-size:2rem;margin-bottom:10px;position:relative;display:inline-block}
.section-title h2::after{content:'';position:absolute;bottom:-8px;left:50%;transform:translateX(-50%);width:60px;height:3px;background:linear-gradient(90deg,#FF4757,#6C5CE7);border-radius:2px}
.section-title p{color:#636e72;font-size:1.05rem;margin-top:16px}
.section-dark .section-title p{color:rgba(255,255,255,.7)}

/* ============ Video Cards Grid ============ */
.video-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:24px}
.video-card{background:#fff;border-radius:14px;overflow:hidden;box-shadow:0 4px 20px rgba(0,0,0,.08);transition:transform .3s,box-shadow .3s}
.video-card:hover{transform:translateY(-6px);box-shadow:0 12px 35px rgba(0,0,0,.15)}
.video-thumb{position:relative;padding-top:56.25%;overflow:hidden;background:#1E3A5F}
.video-thumb img{position:absolute;inset:0;width:100%;height:100%;object-fit:cover;transition:transform .4s}
.video-card:hover .video-thumb img{transform:scale(1.06)}
.play-btn{position:absolute;top:50%;left:50%;transform:translate(-50%,-50%);width:60px;height:60px;background:rgba(255,71,87,.9);border-radius:50%;display:flex;align-items:center;justify-content:center;opacity:0;transition:opacity .3s,transform .3s;cursor:pointer;z-index:3}
.play-btn::after{content:'';border-left:20px solid #fff;border-top:12px solid transparent;border-bottom:12px solid transparent;margin-left:4px}
.video-card:hover .play-btn{opacity:1;transform:translate(-50%,-50%) scale(1.05)}
.video-duration{position:absolute;bottom:8px;right:8px;background:rgba(0,0,0,.75);color:#fff;padding:2px 8px;border-radius:4px;font-size:.78rem;font-weight:600;z-index:2}
.video-info{padding:16px 18px}
.video-info h4{font-size:1.05rem;margin-bottom:6px;display:-webkit-box;-webkit-line-clamp:2;-webkit-box-orient:vertical;overflow:hidden}
.video-desc{color:#636e72;font-size:.88rem;margin-bottom:8px;display:-webkit-box;-webkit-line-clamp:2;-webkit-box-orient:vertical;overflow:hidden}
.video-meta{display:flex;gap:14px;color:#b2bec3;font-size:.85rem}
.video-meta span{display:flex;align-items:center;gap:4px}
.video-tags{display:flex;gap:6px;margin-top:8px;flex-wrap:wrap}
.video-tags span{background:#f0f2f5;color:#636e72;padding:3px 10px;border-radius:12px;font-size:.78rem}

/* ============ Category Tabs ============ */
.tab-nav{display:flex;gap:8px;justify-content:center;margin-bottom:30px;flex-wrap:wrap}
.tab-nav a{padding:10px 24px;border-radius:25px;background:#eef1f5;color:#636e72;font-weight:600;font-size:.95rem;transition:all .3s}
.tab-nav a:hover,.tab-nav a.active{background:linear-gradient(135deg,#FF4757,#e84118);color:#fff}

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

/* ============ Community Feature Grid ============ */
.community-feature-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:24px}
.feature-card{background:#fff;border-radius:14px;padding:30px 24px;text-align:center;box-shadow:0 4px 20px rgba(0,0,0,.08);transition:transform .3s}
.feature-card:hover{transform:translateY(-4px)}
.feature-icon{font-size:2.8rem;margin-bottom:16px}
.feature-card h4{font-size:1.1rem;margin-bottom:8px;color:#1E3A5F}
.feature-card p{color:#636e72;font-size:.92rem;line-height:1.7}

/* ============ Awards Grid ============ */
.awards-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:24px}
.award-card{background:#fff;border-radius:14px;padding:30px 24px;text-align:center;box-shadow:0 4px 20px rgba(0,0,0,.08);transition:transform .3s}
.award-card:hover{transform:translateY(-4px)}
.award-icon{font-size:2.8rem;margin-bottom:16px}
.award-card h4{font-size:1.05rem;margin-bottom:8px;color:#1E3A5F}
.award-card p{color:#636e72;font-size:.92rem;line-height:1.7}

/* ============ Update Timeline ============ */
.update-timeline{max-width:800px;margin:0 auto}
.update-item{display:flex;gap:20px;padding:18px 0;border-bottom:1px solid #e0e4e8;align-items:flex-start}
.update-item:last-child{border-bottom:none}
.update-date{min-width:80px;background:linear-gradient(135deg,#FF4757,#e84118);color:#fff;padding:8px 14px;border-radius:10px;font-weight:700;font-size:.9rem;text-align:center;white-space:nowrap}
.update-content h5{font-size:1.05rem;color:#1E3A5F;margin-bottom:4px}
.update-content p{color:#636e72;font-size:.92rem}

/* ============ Expert Cards ============ */
.expert-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:24px}
.expert-card{background:#fff;border-radius:14px;padding:30px 24px;text-align:center;box-shadow:0 4px 20px rgba(0,0,0,.08);transition:transform .3s}
.expert-card:hover{transform:translateY(-4px)}
.expert-avatar{width:100px;height:100px;border-radius:50%;margin:0 auto 16px;overflow:hidden;border:3px solid #FF4757}
.expert-avatar img{width:100%;height:100%;object-fit:cover}
.expert-card h4{font-size:1.1rem;margin-bottom:4px}
.expert-card .role{color:#FF4757;font-size:.9rem;font-weight:600;margin-bottom:10px}
.expert-card p{color:#636e72;font-size:.9rem;margin-bottom:16px}
.expert-links{display:flex;gap:10px;justify-content:center}
.expert-links a{padding:8px 18px;border-radius:20px;font-size:.85rem;font-weight:600}
.expert-links .link-contact{background:#FF4757;color:#fff}
.expert-links .link-work{background:#eef1f5;color:#1E3A5F}

/* ============ FAQ Section ============ */
.faq-list{max-width:800px;margin:0 auto}
.faq-item{background:#fff;border-radius:12px;margin-bottom:12px;box-shadow:0 2px 12px rgba(0,0,0,.06);overflow:hidden}
.faq-question{padding:18px 24px;font-weight:700;cursor:pointer;display:flex;justify-content:space-between;align-items:center;font-size:1.02rem;color:#1E3A5F;transition:background .3s}
.faq-question:hover{background:#f8f9fa}
.faq-question::after{content:'+';font-size:1.4rem;color:#FF4757;transition:transform .3s}
.faq-item.active .faq-question::after{transform:rotate(45deg)}
.faq-answer{padding:0 24px;max-height:0;overflow:hidden;transition:max-height .4s ease,padding .4s ease;color:#636e72;font-size:.95rem;line-height:1.8}
.faq-item.active .faq-answer{max-height:300px;padding:0 24px 18px}

/* ============ Reviews ============ */
.review-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(300px,1fr));gap:20px}
.review-card{background:#fff;border-radius:14px;padding:24px;box-shadow:0 4px 16px rgba(0,0,0,.06)}
.review-header{display:flex;align-items:center;gap:12px;margin-bottom:12px}
.review-avatar{width:48px;height:48px;border-radius:50%;background:linear-gradient(135deg,#FF4757,#6C5CE7);display:flex;align-items:center;justify-content:center;color:#fff;font-weight:700;font-size:1.1rem;flex-shrink:0}
.review-name{font-weight:700;font-size:1rem}
.review-date{color:#b2bec3;font-size:.82rem}
.review-stars{color:#f39c12;margin-bottom:8px;font-size:1.1rem;letter-spacing:2px}
.review-text{color:#636e72;font-size:.95rem;line-height:1.7}

/* ============ Partner Logos ============ */
.partner-wall{display:flex;flex-wrap:wrap;gap:24px;justify-content:center;align-items:center}
.partner-wall .partner-item{background:#fff;padding:18px 30px;border-radius:12px;box-shadow:0 2px 12px rgba(0,0,0,.06);font-weight:700;color:#1E3A5F;font-size:1rem;transition:transform .3s}
.partner-wall .partner-item:hover{transform:scale(1.05)}

/* ============ Contact Section ============ */
.contact-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:24px}
.contact-card{background:#fff;border-radius:14px;padding:28px;text-align:center;box-shadow:0 4px 16px rgba(0,0,0,.06)}
.section-dark .contact-card{background:rgba(255,255,255,.08);box-shadow:none}
.section-dark .contact-card h4{color:#fff}
.section-dark .contact-card p{color:rgba(255,255,255,.7)}
.contact-card h4{margin-bottom:12px;color:#1E3A5F}
.contact-card p{color:#636e72;font-size:.95rem}
.contact-card .icon{font-size:2.2rem;margin-bottom:12px}

/* ============ How-To Guide ============ */
.howto-steps{display:grid;grid-template-columns:repeat(auto-fill,minmax(240px,1fr));gap:24px;counter-reset:step}
.howto-step{background:#fff;border-radius:14px;padding:30px 24px;text-align:center;box-shadow:0 4px 16px rgba(0,0,0,.06);position:relative;counter-increment:step}
.howto-step::before{content:counter(step);position:absolute;top:-14px;left:50%;transform:translateX(-50%);width:36px;height:36px;background:linear-gradient(135deg,#FF4757,#e84118);color:#fff;border-radius:50%;display:flex;align-items:center;justify-content:center;font-weight:800;font-size:1.1rem}
.howto-step h4{margin-top:10px;margin-bottom:8px}
.howto-step p{color:#636e72;font-size:.92rem}

/* ============ Social Share ============ */
.share-bar{display:flex;gap:12px;justify-content:center;flex-wrap:wrap;padding:20px 0}
.share-btn{display:inline-flex;align-items:center;gap:6px;padding:10px 22px;border-radius:25px;color:#fff;font-weight:600;font-size:.9rem;transition:transform .3s;cursor:pointer;border:none}
.share-btn:hover{transform:translateY(-2px);color:#fff}
.share-wechat{background:#07C160}
.share-weibo{background:#E6162D}
.share-douyin{background:#161823}
.share-bilibili{background:#00A1D6}

/* ============ Footer ============ */
.site-footer{background:#0d1b2a;color:rgba(255,255,255,.7);padding:50px 0 0}
.footer-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(220px,1fr));gap:30px;margin-bottom:30px}
.footer-col h4{color:#fff;margin-bottom:16px;font-size:1.05rem}
.footer-col p,.footer-col a{color:rgba(255,255,255,.6);font-size:.92rem;line-height:2}
.footer-col a:hover{color:#FF4757}
.footer-col .qr-img{width:120px;border-radius:8px;margin-top:8px}
.footer-logo{margin-bottom:8px}
.footer-links{text-align:center;padding:16px 0;border-top:1px solid rgba(255,255,255,.08);border-bottom:1px solid rgba(255,255,255,.08);margin-bottom:0}
.footer-links a{color:rgba(255,255,255,.5);font-size:.88rem;margin:0 6px;transition:color .3s}
.footer-links a:hover{color:#FF4757}
.footer-bottom{padding:20px 0;text-align:center;font-size:.88rem}
.footer-bottom .update-time{color:#FF4757;font-weight:600}

/* ============ Breadcrumb ============ */
.breadcrumb{padding:14px 0;font-size:.9rem;color:#b2bec3}
.breadcrumb a{color:#636e72}
.breadcrumb a:hover{color:#FF4757}
.breadcrumb span{margin:0 8px;color:#dfe6e9}

/* ============ Inner Page Banner ============ */
.page-banner{background:linear-gradient(135deg,#1E3A5F 0%,#6C5CE7 100%);padding:50px 0;text-align:center}
.page-banner h1{color:#fff;font-size:2.2rem;margin-bottom:8px}
.page-banner p{color:rgba(255,255,255,.8);font-size:1.05rem}

/* ============ Responsive ============ */
@media(max-width:992px){
  .video-grid,.service-grid,.community-feature-grid,.awards-grid{grid-template-columns:repeat(2,1fr)}
  .hero-content h1{font-size:2rem}
  .main-nav{display:none;position:absolute;top:100%;left:0;right:0;background:#1E3A5F;flex-direction:column;padding:16px;box-shadow:0 8px 20px rgba(0,0,0,.2)}
  .main-nav.open{display:flex}
  .main-nav a{padding:12px 16px;width:100%}
  .mobile-toggle{display:block}
}
@media(max-width:640px){
  .video-grid,.service-grid,.community-feature-grid,.awards-grid{grid-template-columns:1fr}
  .hero-content h1{font-size:1.6rem}
  .hero-content p{font-size:1rem}
  .section{padding:40px 0}
  .section-title h2{font-size:1.5rem}
  .search-wrap{flex-direction:column;gap:0}
  .search-wrap input{border-radius:25px 25px 0 0}
  .search-wrap button{border-radius:0 0 25px 25px}
  .footer-grid{grid-template-columns:1fr 1fr}
  .expert-grid{grid-template-columns:1fr}
  .review-grid{grid-template-columns:1fr}
  .update-item{flex-direction:column;gap:10px}
  .update-date{min-width:auto;display:inline-block}
}

/* ============ Animations ============ */
@keyframes fadeInUp{from{opacity:0;transform:translateY(30px)}to{opacity:1;transform:translateY(0)}}
.fade-in{opacity:0;animation:fadeInUp .6s ease forwards}
.delay-1{animation-delay:.1s}
.delay-2{animation-delay:.2s}
.delay-3{animation-delay:.3s}

/* ============ Utility ============ */
.text-center{text-align:center}
.mt-20{margin-top:20px}
.mb-20{margin-bottom:20px}
.text-red{color:#FF4757}
.text-purple{color:#6C5CE7}
.bg-gradient{background:linear-gradient(135deg,#FF4757 0%,#6C5CE7 100%)}