:root{--primary-color:#0284c7;--primary-hover:#0369a1;--primary-light:#e0f2fe;--primary-dark:#075985;--accent-orange:#f97316;--accent-green:#10b981;--accent-purple:#8b5cf6;--bg-main:#f8fafc;--bg-card:#fff;--text-main:#1e293b;--text-muted:#64748b;--border-color:#e2e8f0;--shadow-sm:0 1px 2px 0 #0000000d;--shadow-md:0 4px 6px -1px #0000001a, 0 2px 4px -2px #0000001a;--shadow-lg:0 10px 15px -3px #0000001a, 0 4px 6px -4px #0000001a;--radius:8px}*{box-sizing:border-box;margin:0;padding:0}body{background-color:var(--bg-main);color:var(--text-main);-webkit-font-smoothing:antialiased;font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,PingFang SC,Hiragino Sans GB,Microsoft YaHei,sans-serif;line-height:1.5}.site-header{color:#fff;z-index:100;background:linear-gradient(135deg,#0284c7 0%,#0369a1 100%);position:sticky;top:0;box-shadow:0 2px 8px #00000026}.header-inner{justify-content:space-between;align-items:center;gap:20px;max-width:1400px;margin:0 auto;padding:12px 24px;display:flex}.brand-area{cursor:pointer;align-items:center;gap:12px;display:flex}.brand-logo{background:#fff;border-radius:10px;justify-content:center;align-items:center;width:44px;height:44px;font-size:24px;display:flex;box-shadow:0 2px 6px #0003}.brand-text h1{letter-spacing:.5px;font-size:20px;font-weight:700;line-height:1.2}.brand-text p{opacity:.9;font-size:11px;font-weight:400}.header-nav{gap:20px;margin-left:20px;display:flex}.header-nav a{color:#fff;opacity:.9;border-radius:6px;padding:6px 12px;font-size:14px;font-weight:500;text-decoration:none;transition:all .2s}.header-nav a:hover,.header-nav a.active{opacity:1;background:#fff3}.header-actions{align-items:center;gap:12px;margin-left:auto;display:flex}.search-box{align-items:center;display:flex;position:relative}.search-box input{color:#fff;background:#ffffff26;border:1px solid #fff6;border-radius:20px;outline:none;width:240px;padding:8px 36px 8px 14px;font-size:13px;transition:all .2s}.search-box input::placeholder{color:#ffffffb3}.search-box input:focus{color:var(--text-main);background:#fff;border-color:#fff;width:280px}.search-box input:focus::placeholder{color:#94a3b8}.search-icon{color:#fffc;pointer-events:none;font-size:14px;position:absolute;right:12px}.search-box input:focus~.search-icon{color:var(--primary-color)}.btn-upload{color:#78350f;cursor:pointer;background:#fbbf24;border:none;border-radius:20px;align-items:center;gap:6px;padding:8px 16px;font-size:13px;font-weight:600;transition:all .2s;display:flex;box-shadow:0 2px 6px #fbbf244d}.btn-upload:hover{background:#f59e0b;transform:translateY(-1px)}.main-layout{align-items:flex-start;gap:24px;max-width:1400px;margin:20px auto;padding:0 24px;display:flex}.sidebar{background:var(--bg-card);border-radius:var(--radius);border:1px solid var(--border-color);width:260px;box-shadow:var(--shadow-sm);flex-shrink:0;position:sticky;top:80px;overflow:hidden}.sidebar-header{border-bottom:1px solid var(--border-color);background:#f0f9ff;justify-content:space-between;align-items:center;padding:14px 18px;display:flex}.sidebar-header h2{color:var(--primary-dark);align-items:center;gap:8px;font-size:15px;font-weight:700;display:flex}.sidebar-count{background:var(--primary-light);color:var(--primary-color);border-radius:10px;padding:2px 8px;font-size:11px;font-weight:600}.category-list{padding:8px;list-style:none}.category-item{cursor:pointer;color:#334155;border-radius:6px;justify-content:space-between;align-items:center;margin-bottom:2px;padding:10px 12px;font-size:13.5px;transition:all .2s;display:flex}.category-item:hover{color:var(--primary-color);background:#f1f5f9}.category-item.active{background:var(--primary-light);color:var(--primary-dark);font-weight:600}.category-left{align-items:center;gap:8px;display:flex}.category-icon{font-size:16px}.category-badge{color:#94a3b8;font-size:11px}.category-item.active .category-badge{color:var(--primary-color);font-weight:600}.content-area{flex:1;min-width:0}.filter-card{background:var(--bg-card);border-radius:var(--radius);border:1px solid var(--border-color);box-shadow:var(--shadow-sm);margin-bottom:20px;padding:16px 20px}.filter-row{align-items:center;gap:16px;margin-bottom:12px;display:flex}.filter-row:last-child{border-top:1px dashed var(--border-color);margin-bottom:0;padding-top:12px}.filter-label{color:#475569;text-align:right;flex-shrink:0;width:70px;font-size:13px;font-weight:600}.filter-tags{flex-wrap:wrap;flex:1;gap:8px;display:flex}.filter-tag{cursor:pointer;color:#475569;background:0 0;border:1px solid #0000;border-radius:16px;padding:4px 14px;font-size:13px;transition:all .2s}.filter-tag:hover{color:var(--primary-color);background:#f8fafc}.filter-tag.active{background:var(--primary-color);color:#fff;font-weight:500;box-shadow:0 2px 4px #0284c740}.toolbar-row{justify-content:space-between;align-items:center;margin-bottom:16px;padding:0 4px;display:flex}.result-stat{color:var(--text-muted);font-size:13px}.result-stat strong{color:var(--primary-color);font-weight:600}.sort-group{gap:8px;display:flex}.sort-btn{border:1px solid var(--border-color);color:#64748b;cursor:pointer;background:#fff;border-radius:4px;padding:4px 10px;font-size:12px}.sort-btn.active{color:var(--primary-color);border-color:var(--primary-color);background:var(--primary-light);font-weight:600}.card-list{flex-direction:column;gap:14px;display:flex}.course-card{background:var(--bg-card);border-radius:var(--radius);border:1px solid var(--border-color);box-shadow:var(--shadow-sm);align-items:center;gap:20px;padding:16px 20px;transition:all .2s;display:flex;position:relative}.course-card:hover{box-shadow:var(--shadow-md);border-color:#bae6fd;transform:translateY(-2px)}.card-cover{background:#e2e8f0;border-radius:6px;flex-shrink:0;width:160px;height:96px;position:relative;overflow:hidden}.card-cover img{object-fit:cover;width:100%;height:100%;transition:transform .3s}.course-card:hover .card-cover img{transform:scale(1.05)}.type-badge{color:#fff;-webkit-backdrop-filter:blur(4px);backdrop-filter:blur(4px);border-radius:4px;padding:2px 8px;font-size:11px;font-weight:600;position:absolute;top:6px;left:6px;box-shadow:0 1px 3px #0000004d}.badge-video{background:#0284c7e6}.badge-doc{background:#10b981e6}.badge-game{background:#8b5cf6e6}.card-info{flex:1;min-width:0}.card-title{color:#1e293b;white-space:nowrap;text-overflow:ellipsis;cursor:pointer;margin-bottom:8px;font-size:16px;font-weight:600;overflow:hidden}.card-title:hover{color:var(--primary-color)}.card-meta{color:#64748b;align-items:center;gap:12px;margin-bottom:6px;font-size:12.5px;display:flex}.card-tag{color:#475569;background:#f1f5f9;border-radius:4px;padding:2px 8px}.card-tag.grade-tag{color:#b45309;background:#fef3c7;font-weight:500}.card-summary{color:#94a3b8;-webkit-line-clamp:1;-webkit-box-orient:vertical;font-size:12px;display:-webkit-box;overflow:hidden}.card-action{flex-shrink:0}.btn-enter{color:#fff;cursor:pointer;background:#0284c7;border:none;border-radius:6px;padding:9px 20px;font-size:13.5px;font-weight:600;transition:all .2s;box-shadow:0 2px 4px #0284c733}.btn-enter:hover{background:#0369a1;transform:scale(1.03)}.empty-state{border-radius:var(--radius);border:1px dashed var(--border-color);text-align:center;color:var(--text-muted);background:#fff;padding:60px 20px}.empty-state span{margin-bottom:12px;font-size:40px;display:block}.modal-backdrop{-webkit-backdrop-filter:blur(4px);backdrop-filter:blur(4px);z-index:999;opacity:0;pointer-events:none;background:#0f172a99;justify-content:center;align-items:center;padding:20px;transition:opacity .2s;display:flex;position:fixed;inset:0}.modal-backdrop.show{opacity:1;pointer-events:auto}.modal-content{width:100%;max-width:900px;max-height:90vh;box-shadow:var(--shadow-lg);background:#fff;border-radius:12px;flex-direction:column;transition:transform .2s;display:flex;overflow:hidden;transform:translateY(20px)}.modal-backdrop.show .modal-content{transform:translateY(0)}.modal-header{border-bottom:1px solid var(--border-color);background:#f8fafc;justify-content:space-between;align-items:center;padding:16px 24px;display:flex}.modal-title{color:#1e293b;align-items:center;gap:10px;font-size:17px;font-weight:700;display:flex}.modal-close{color:#94a3b8;cursor:pointer;background:0 0;border:none;border-radius:4px;justify-content:center;align-items:center;width:32px;height:32px;font-size:24px;line-height:1;transition:all .2s;display:flex}.modal-close:hover{color:#0f172a;background:#f1f5f9}.modal-body{flex:1;padding:24px;overflow-y:auto}.video-container{aspect-ratio:16/9;background:#000;border-radius:8px;width:100%;margin-bottom:16px;overflow:hidden}.video-container video,.video-container iframe{border:none;width:100%;height:100%}.video-meta-box{border:1px solid var(--border-color);background:#f8fafc;border-radius:8px;padding:16px}.doc-reader{flex-direction:column;gap:20px;display:flex}.doc-pages-nav{border-bottom:1px solid var(--border-color);gap:8px;padding-bottom:8px;display:flex;overflow-x:auto}.doc-page-btn{border:1px solid var(--border-color);cursor:pointer;white-space:nowrap;background:#fff;border-radius:6px;padding:6px 14px;font-size:13px}.doc-page-btn.active{background:var(--primary-color);color:#fff;border-color:var(--primary-color)}.doc-page-content{background:#fffdf9;border:1px solid #f1e7d0;border-radius:8px;min-height:300px;padding:28px 32px;box-shadow:inset 0 0 10px #00000005}.doc-page-title{color:#854d0e;border-bottom:2px solid #fef08a;margin-bottom:16px;padding-bottom:8px;font-size:18px;font-weight:700}.doc-page-text{color:#334155;white-space:pre-line;font-size:15px;line-height:1.8}.quiz-game{background:linear-gradient(135deg,#f3e8ff 0%,#ede9fe 100%);border:2px solid #c084fc;border-radius:12px;padding:24px}.quiz-progress{color:#6b21a8;justify-content:space-between;margin-bottom:16px;font-size:14px;font-weight:600;display:flex}.quiz-question-box{color:#1e1b4b;background:#fff;border-radius:10px;margin-bottom:20px;padding:20px;font-size:16px;font-weight:600;box-shadow:0 4px 6px #0000000d}.quiz-options{flex-direction:column;gap:10px;display:flex}.quiz-option{cursor:pointer;text-align:left;background:#fff;border:1px solid #d8b4fe;border-radius:8px;padding:12px 18px;font-size:14px;transition:all .2s}.quiz-option:hover{background:#faf5ff;border-color:#a855f7}.quiz-option.correct{color:#15803d;background:#dcfce7;border-color:#22c55e;font-weight:600}.quiz-option.wrong{color:#b91c1c;background:#fee2e2;border-color:#ef4444}.quiz-feedback{background:#fff;border-radius:8px;margin-top:16px;padding:12px 16px;font-size:13px;line-height:1.6}.form-grid{grid-template-columns:1fr 1fr;gap:16px;display:grid}.form-group{flex-direction:column;gap:6px;display:flex}.form-group.full{grid-column:1/-1}.form-group label{color:#475569;font-size:13px;font-weight:600}.form-group input,.form-group select,.form-group textarea{border:1px solid var(--border-color);border-radius:6px;outline:none;padding:9px 12px;font-family:inherit;font-size:13.5px;transition:border-color .2s}.form-group input:focus,.form-group select:focus,.form-group textarea:focus{border-color:var(--primary-color);box-shadow:0 0 0 3px #0284c726}.modal-footer{border-top:1px solid var(--border-color);background:#f8fafc;justify-content:flex-end;gap:12px;padding:16px 24px;display:flex}.btn-secondary{border:1px solid var(--border-color);color:#475569;cursor:pointer;background:#fff;border-radius:6px;padding:8px 18px;font-size:13px;font-weight:500}.btn-primary{background:var(--primary-color);color:#fff;cursor:pointer;border:none;border-radius:6px;padding:8px 20px;font-size:13px;font-weight:600}.btn-primary:hover{background:var(--primary-hover)}.site-footer{border-top:1px solid var(--border-color);color:#94a3b8;text-align:center;background:#fff;margin-top:40px;padding:24px;font-size:12px;line-height:1.8}.site-footer strong{color:#64748b}@media (width<=900px){.main-layout{flex-direction:column;padding:0 16px}.sidebar{width:100%;position:static}.search-box input{width:140px}.search-box input:focus{width:180px}.form-grid{grid-template-columns:1fr}}.upload-box-container{background:#f8fafc;border:1px solid #e2e8f0;border-radius:8px;padding:12px}.file-drop-area{text-align:center;cursor:pointer;background:#fff;border:2px dashed #cbd5e1;border-radius:8px;padding:16px 20px;transition:all .2s}.file-drop-area:hover,.file-drop-area.dragover{border-color:var(--primary-color);background:#f0f9ff}.file-drop-content{flex-direction:column;align-items:center;gap:8px;display:flex}.upload-icon{font-size:28px}.upload-text{color:#64748b;font-size:13px}.btn-file-select{color:#334155;cursor:pointer;background:#e2e8f0;border:none;border-radius:6px;padding:5px 14px;font-size:12px;font-weight:600;transition:all .2s}.btn-file-select:hover{color:#0f172a;background:#cbd5e1}.cover-preview-box{background:#fff;border:1px solid #e2e8f0;border-radius:6px;align-items:center;gap:16px;padding:8px;display:flex}.cover-preview-box img{object-fit:cover;border:1px solid #e2e8f0;border-radius:4px;width:100px;height:60px}.cover-preview-info{color:#334155;text-align:left;flex-direction:column;gap:6px;font-size:12.5px;display:flex}.btn-remove-file{color:#b91c1c;cursor:pointer;background:#fee2e2;border:none;border-radius:4px;width:fit-content;padding:3px 8px;font-size:11.5px}.btn-remove-file:hover{background:#fca5a5}.file-selected-box{background:#ecfdf5;border:1px solid #a7f3d0;border-radius:6px;justify-content:space-between;align-items:center;padding:8px 12px;display:flex}.file-info-row{color:#065f46;align-items:center;gap:10px;font-size:13px;display:flex}.file-badge{color:#fff;background:#10b981;border-radius:4px;padding:2px 6px;font-size:11px;font-weight:600}.file-size{color:#059669;font-size:12px}