:root{--brand:#FF6B35;--dark:#1F2937;--bg:#F7F8FA;--line:#E8ECF1;--muted:#8A94A6}
*{box-sizing:border-box}
body{margin:0;font-family:-apple-system,"Segoe UI","Microsoft YaHei",sans-serif;background:var(--bg);color:#222}
a{color:inherit;text-decoration:none}
.nav{background:var(--dark);color:#fff;position:sticky;top:0;z-index:50}
.nav-inner{max-width:1160px;margin:0 auto;display:flex;align-items:center;gap:22px;padding:0 18px;height:60px}
.brand{display:flex;align-items:center;gap:10px;font-weight:700;font-size:17px}
.logo{width:30px;height:30px;border-radius:8px;background:var(--brand);display:flex;align-items:center;justify-content:center;font-size:16px}
.nav-links{display:flex;gap:18px;flex:1}
.nav-links a{opacity:.85;padding:6px 2px;border-bottom:2px solid transparent}
.nav-links a.active,.nav-links a:hover{opacity:1;border-color:var(--brand)}
.nav-right{display:flex;align-items:center;gap:10px}
.lang-sel{background:#2B3648;color:#fff;border:1px solid #3A4658;border-radius:8px;padding:6px 8px}
.container{max-width:1160px;margin:0 auto;padding:24px 18px 60px;min-height:60vh}
.foot{border-top:1px solid var(--line);color:var(--muted);text-align:center;padding:22px;font-size:13px}
.btn{display:inline-block;border:0;border-radius:9px;padding:9px 16px;font-size:14px;cursor:pointer;line-height:1.2}
.btn-primary{background:var(--brand);color:#fff}
.btn-ghost{background:transparent;border:1px solid #CBD5E1;color:inherit}
.btn-lg{padding:12px 26px;font-size:16px}
.btn-block{width:100%;display:block}
.hero{background:linear-gradient(135deg,#1F2937,#374151);color:#fff;border-radius:16px;padding:52px 34px;margin-bottom:26px}
.hero h1{margin:0 0 10px;font-size:30px}
.hero p{color:#CBD5E1;margin:0 0 20px}
.sec-title{font-size:19px;margin:26px 0 14px}
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:16px}
.card{background:#fff;border:1px solid var(--line);border-radius:14px;overflow:hidden;display:block}
.card-cover{height:132px;background:#EEF1F5 center/cover no-repeat}
.card-body{padding:14px}
.card-title{font-weight:600;margin-bottom:6px}
.card-sub,.muted{color:var(--muted);font-size:13px}
.card-price{color:var(--brand);font-weight:700;margin-top:8px}
.empty,.muted.center{text-align:center;color:var(--muted);padding:26px 0}
.filters{display:flex;gap:10px;margin-bottom:16px;flex-wrap:wrap}
.input{border:1px solid var(--line);border-radius:9px;padding:10px 12px;font-size:14px;width:100%;background:#fff}
.filters .input{width:auto;min-width:150px}
.form-wrap{max-width:420px;margin:30px auto;background:#fff;border:1px solid var(--line);border-radius:14px;padding:26px}
.form-wrap h2{margin:0 0 16px}
.form-wrap .input{margin-bottom:12px}
.radio-row{display:flex;gap:18px;margin-bottom:12px}
.kv{display:flex;justify-content:space-between;padding:9px 0;border-bottom:1px dashed var(--line)}
.row-actions{display:flex;gap:10px;margin-top:12px;flex-wrap:wrap}
.warn{background:#FFF4E5;border:1px solid #FFD9A8;color:#8A5A00;border-radius:10px;padding:10px 14px}
.modal-mask{position:fixed;inset:0;background:rgba(15,23,42,.45);display:flex;align-items:center;justify-content:center;z-index:80}
.modal{background:#fff;border-radius:14px;padding:22px;min-width:330px;max-width:92vw}
.modal-sub,.small{font-size:13px;color:var(--muted)}
.pay-opt{display:block;padding:9px 6px;border-bottom:1px solid var(--line)}
.modal-actions{display:flex;gap:10px;justify-content:flex-end;margin-top:16px}
.detail-head{display:flex;gap:20px;flex-wrap:wrap}
.detail-cover{width:320px;height:190px;border-radius:14px;background:#EEF1F5 center/cover no-repeat}
.detail-info{flex:1;min-width:260px}
.price-lg{color:var(--brand);font-size:24px;font-weight:700;margin:10px 0}
.detail-text{background:#fff;border:1px solid var(--line);border-radius:12px;padding:14px;white-space:pre-wrap;font-family:inherit}
.mat-list{list-style:none;padding:0;margin:0}
.mat-list li{background:#fff;border:1px solid var(--line);border-radius:10px;padding:10px 12px;margin-bottom:8px;display:flex;gap:10px;align-items:center}
.mat-row{cursor:pointer}
.mat-row:hover{border-color:var(--brand)}
.tag{background:#EEF2FF;color:#3B5BDB;border-radius:6px;padding:2px 7px;font-size:12px}
.learn-wrap{display:flex;gap:18px;flex-wrap:wrap}
.learn-side{width:280px;flex:0 0 auto}
.learn-main{flex:1;min-width:300px}
.viewer{background:#fff;border:1px solid var(--line);border-radius:12px;min-height:520px;overflow:hidden}
.pdf{width:100%;height:78vh;border:0}
.video{width:100%;max-height:78vh;background:#000}
.img{max-width:100%;display:block}
.wm-layer{position:fixed;inset:0;pointer-events:none;z-index:70}
.wm-layer span{position:absolute;color:rgba(120,120,120,.30);font-size:14px;white-space:nowrap;transform:rotate(-20deg);user-select:none}
.stu-list{max-height:320px;overflow:auto}
.stu-row{display:flex;justify-content:space-between;padding:8px 0;border-bottom:1px dashed var(--line)}
.teachers .card{display:block}
@media(max-width:720px){.nav-links{display:none}.hero{padding:32px 20px}.hero h1{font-size:23px}}