:root{--bg: #ffffff;--bg-soft: #f8fafc;--bg-tint: #eff6ff;--ink: #111827;--ink-2: #374151;--ink-3: #6b7280;--primary: #2563eb;--primary-deep: #1d4ed8;--line: #e5e7eb;--line-strong: #d1d5db;--white: #ffffff;--font-sans: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;--font-num: "Helvetica Neue", Arial, sans-serif;--radius: 8px;--shadow: 0 10px 24px -12px rgba(17, 24, 39, .18);--shadow-lg: 0 20px 40px -18px rgba(17, 24, 39, .22)}*{margin:0;padding:0;box-sizing:border-box}html{scroll-behavior:smooth}body{background:var(--bg);color:var(--ink);font-family:var(--font-sans);font-size:14px;line-height:1.65;-webkit-font-smoothing:antialiased}a{color:inherit;text-decoration:none}button{font-family:inherit;cursor:pointer}.site-header{position:sticky;top:0;z-index:50;background:#fffffff0;-webkit-backdrop-filter:blur(10px);backdrop-filter:blur(10px);border-bottom:1px solid var(--line)}.header-inner{max-width:1320px;margin:0 auto;width:100%;display:flex;align-items:center;gap:28px;padding:12px 40px}.brand{display:flex;align-items:baseline;gap:10px;font-weight:900;font-size:20px;letter-spacing:1px;white-space:nowrap;color:var(--ink)}.brand .en{font-family:var(--font-num);font-size:11px;letter-spacing:3px;color:var(--primary);text-transform:uppercase;font-weight:700}.nav-cates{display:flex;gap:4px;overflow-x:auto;scrollbar-width:none;flex:1;justify-content:center}.nav-cates::-webkit-scrollbar{display:none}.nav-cates a{font-size:13px;color:var(--ink-2);padding:6px 14px;border-radius:999px;white-space:nowrap;transition:color .2s,background .2s}.nav-cates a:hover{color:var(--primary);background:var(--bg-tint)}.nav-cates a.on{color:var(--white);background:var(--primary);font-weight:700}.site-header-detail .header-inner{justify-content:space-between}.back-home{font-size:13px;font-weight:600;color:var(--primary);padding:6px 18px;border:1px solid var(--primary);border-radius:999px;transition:all .2s}.back-home:hover{background:var(--primary);color:var(--white)}.page-home{max-width:1320px;margin:0 auto;padding:0 40px 90px}.cate-section{padding:48px 0 26px;border-top:1px solid var(--line)}.cate-section:first-of-type{border-top:none}.section-head{display:flex;align-items:flex-end;gap:18px;margin-bottom:22px}.section-index{font-family:var(--font-num);font-size:56px;line-height:.9;font-weight:800;color:transparent;-webkit-text-stroke:1.5px var(--primary);-webkit-user-select:none;user-select:none}.section-title{font-size:30px;font-weight:900;letter-spacing:1px;color:var(--ink)}.section-count{color:var(--ink-3);font-size:12px;letter-spacing:1px;margin-bottom:2px}.section-meta{display:flex;flex-direction:column;gap:2px;margin-left:auto;text-align:right}.sub-tags{display:flex;flex-wrap:wrap;gap:8px;margin-bottom:20px}.sub-tags button{border:1px solid var(--line);background:var(--white);color:var(--ink-2);font-size:12.5px;padding:4px 14px;border-radius:999px;transition:all .2s}.sub-tags button:hover{border-color:var(--primary);color:var(--primary);background:var(--bg-tint)}.sub-tags button.on{background:var(--primary);border-color:var(--primary);color:var(--white);font-weight:700}.lesson-grid{display:grid;grid-template-columns:repeat(5,1fr);gap:20px}@media (max-width: 1180px){.lesson-grid{grid-template-columns:repeat(4,1fr)}}@media (max-width: 900px){.lesson-grid{grid-template-columns:repeat(2,1fr)}}.lesson-card{display:block;position:relative;overflow:hidden;background:var(--white);border:1px solid var(--line);border-radius:var(--radius);cursor:pointer;transition:border-color .2s,box-shadow .2s;animation:cardIn .35s ease both}.lesson-card:hover{border-color:var(--primary);box-shadow:var(--shadow-lg)}@keyframes cardIn{0%{opacity:0;transform:translateY(10px)}to{opacity:1;transform:none}}.card-cover{position:relative;aspect-ratio:16/9;background:var(--bg-soft);overflow:hidden}.card-cover img{width:100%;height:100%;object-fit:cover;display:block}.card-body{padding:12px 14px 14px}.card-name{font-weight:700;font-size:14.5px;line-height:1.5;color:var(--ink);height:3em;overflow:hidden;display:-webkit-box;-webkit-line-clamp:2;-webkit-box-orient:vertical}.lesson-card:hover .card-name{color:var(--primary-deep)}.card-meta{margin-top:8px;display:flex;justify-content:space-between;align-items:center}.card-teacher{color:var(--ink-3);font-size:12px;overflow:hidden;text-overflow:ellipsis;white-space:nowrap;max-width:60%}.card-tag{font-size:11px;color:var(--primary);background:var(--bg-tint);padding:1px 8px;border-radius:999px;white-space:nowrap}.pager{display:flex;justify-content:center;align-items:center;gap:6px;margin-top:26px}.pager button{min-width:34px;height:34px;padding:0 10px;background:var(--white);border:1px solid var(--line);color:var(--ink-2);border-radius:var(--radius);font-size:13px;transition:all .2s}.pager button:hover:not(:disabled){border-color:var(--primary);color:var(--primary)}.pager button.on{background:var(--primary);border-color:var(--primary);color:var(--white);font-weight:700}.pager button:disabled{opacity:.4;cursor:not-allowed}.state-box{text-align:center;padding:60px 20px;color:var(--ink-3)}.state-box button{margin-top:14px;background:var(--primary);color:var(--white);border:none;padding:8px 26px;border-radius:var(--radius);font-weight:700;transition:background .2s}.state-box button:hover{background:var(--primary-deep)}.skeleton{height:260px;border-radius:var(--radius);background:linear-gradient(100deg,#f1f5f9 40%,#e2e8f0,#f1f5f9 60%);background-size:200% 100%;animation:shimmer 1.3s infinite}@keyframes shimmer{to{background-position:-200% 0}}.page-detail{max-width:1320px;margin:0 auto;padding:30px 40px 90px}.back-link{display:inline-flex;align-items:center;gap:6px;color:var(--ink-3);font-size:13px;margin-bottom:18px;transition:color .2s}.back-link:hover{color:var(--primary)}.detail-title{font-size:28px;font-weight:900;letter-spacing:1px;line-height:1.5;margin-bottom:20px;color:var(--ink)}.detail-layout{display:grid;grid-template-columns:1fr 360px;gap:28px;align-items:start}@media (max-width: 980px){.detail-layout{grid-template-columns:1fr}}.detail-main{display:flex;flex-direction:column;gap:20px}.player-wrap{background:#000;border-radius:var(--radius);overflow:hidden;box-shadow:var(--shadow-lg)}#player-box{width:100%;aspect-ratio:16 / 9}#player-box>div{width:100%!important;height:100%!important}#player-box .vjs-tech{width:100%!important;height:100%!important}.class-panel{background:var(--white);border:1px solid var(--line);border-radius:var(--radius);padding:16px 0 6px;max-height:720px;overflow-y:auto}.class-panel h3{font-size:15px;font-weight:700;padding:0 20px 12px;letter-spacing:1px;color:var(--ink)}.class-item{display:flex;align-items:center;gap:12px;width:100%;text-align:left;padding:11px 20px;background:transparent;border:none;border-top:1px solid var(--line);color:var(--ink);font-size:13.5px;transition:background .15s}.class-item:hover:not(:disabled){background:var(--bg-tint)}.class-item.on{background:var(--bg-tint);box-shadow:inset 3px 0 0 var(--primary)}.class-item:disabled{color:var(--ink-3);cursor:not-allowed}.class-no-badge{font-family:var(--font-num);font-size:12px;font-weight:700;color:var(--primary);border:1px solid var(--primary);border-radius:6px;padding:0 7px;flex-shrink:0}.class-item:disabled .class-no-badge{color:var(--ink-3);border-color:var(--line-strong)}.class-name{flex:none;width:180px;white-space:normal;word-break:break-all;line-height:1.5;display:-webkit-box;-webkit-line-clamp:2;-webkit-box-orient:vertical;overflow:hidden}.free-tag{font-size:11px;font-weight:700;color:var(--primary);flex-shrink:0;margin-left:auto}.lock-tag{font-size:11px;color:var(--ink-3);flex-shrink:0;display:inline-flex;align-items:center;gap:4px;margin-left:auto}.lock-tag svg{width:12px;height:12px}.lesson-info{background:var(--bg-soft);border:1px solid var(--line);border-radius:var(--radius);padding:18px 24px 22px}.info-row{display:flex;flex-wrap:wrap;gap:10px 22px;color:var(--ink-3);font-size:13px;margin-bottom:4px}.info-row b{color:var(--ink);font-weight:600;margin-right:6px}.info-section{border-top:1px solid var(--line);padding-top:14px;margin-top:14px}.info-section h2{font-size:15px;font-weight:700;color:var(--ink);margin-bottom:8px;letter-spacing:1px;padding-left:8px;border-left:3px solid var(--primary)}.info-section .rich{color:var(--ink-2);font-size:13px;line-height:1.9}.info-section .rich p{margin-bottom:6px}.outline-imgs img{width:100%;border-radius:6px;margin-bottom:10px;display:block}.class-dur{font-size:11.5px;color:var(--ink-3);flex-shrink:0;font-family:var(--font-num)}