.accordion-menu{width:100%;max-height:calc(100vh - 180px);overflow-y:auto;overflow-x:hidden}.accordion-menu::-webkit-scrollbar{width:4px}.accordion-menu::-webkit-scrollbar-track{background:transparent}.accordion-menu::-webkit-scrollbar-thumb{background:transparent!important;border-radius:2px;transition:background .3s ease}.accordion-menu:hover::-webkit-scrollbar-thumb{background:var(--scrollbar-color,rgba(0,0,0,.3))!important}.accordion-menu::-webkit-scrollbar-thumb:hover{background:var(--scrollbar-hover-color,rgba(0,0,0,.5))!important}.accordion-menu{scrollbar-width:thin;scrollbar-color:transparent transparent}.accordion-menu:hover{scrollbar-color:var(--scrollbar-color,rgba(0,0,0,.3)) transparent!important}.accordion-item{border:1px solid #dee2e6;border-bottom:0;background-color:#fff}.accordion-item:last-child{border-bottom:1px solid #dee2e6;border-bottom-left-radius:.375rem;border-bottom-right-radius:.375rem}.accordion-item:first-child{border-top-left-radius:.375rem;border-top-right-radius:.375rem}.accordion-header{width:100%;padding:1rem 1.25rem;font-size:1rem;font-weight:500;text-align:left;color:#495057;background-color:#fafbfc;border:none;cursor:pointer;display:flex;justify-content:space-between;align-items:center;transition:background-color .15s ease-in-out}.accordion-header:hover{background-color:#f1f3f5}.accordion-item.open .accordion-header{background-color:#f1f3f5;border-bottom:1px solid #dee2e6}.accordion-title{font-size:1.6rem;flex:1}.accordion-icon{font-size:1.6rem;font-weight:700;color:#6c757d;min-width:1.5rem;text-align:center}.accordion-content{padding:0;background-color:#fff}.accordion-content a{display:flex;align-items:center;padding:.75rem 1.25rem;color:#495057;text-decoration:none;border-bottom:1px solid #f1f3f5;transition:background-color .15s ease-in-out}.accordion-content a:hover{background-color:#f8f9fa;color:#212529}.accordion-content a.active{background-color:var(--active-bg-color,#e7f3ff);color:var(--active-text-color,#0056b3);font-weight:500;border-left:3px solid var(--active-border-color,#0056b3)}.accordion-content .lesson-no{min-width:3rem;padding:.25rem .5rem;font-weight:600;color:#6c757d;background-color:#f1f3f5;border-radius:.25rem;margin-right:.75rem;text-align:center}.accordion-content a.active .lesson-no{background-color:var(--active-text-color,#0056b3);color:#fff}.accordion-content .lesson-title{flex:1;font-size:1.6rem;line-height:1.5}@media (max-width:768px){.accordion-header{padding:.875rem 1rem;font-size:.95rem}.accordion-content a{padding:.625rem 1rem}.accordion-content .lesson-no{min-width:2.5rem;font-size:.8rem;margin-right:.5rem}.accordion-content .lesson-title{font-size:.85rem}}.accordion-section{border-bottom:1px solid #dee2e6}.accordion-section:last-child{border-bottom:none}.accordion-section>.accordion-header{width:100%;padding:1rem 1.25rem;font-size:1rem;font-weight:600;text-align:left;color:#212529;background-color:#f8f9fa;border:none;border-bottom:1px solid #dee2e6;cursor:pointer;display:flex;justify-content:space-between;align-items:center;transition:background-color .15s ease-in-out}.accordion-section>.accordion-header:hover{background-color:#e9ecef}.accordion-section>.accordion-header .accordion-title{font-size:1.7rem;font-weight:600}.accordion-arrow{font-size:1.2rem;color:#6c757d;transition:transform .2s ease;display:inline-block}.accordion-arrow.open{transform:rotate(180deg)}.era-section{border-bottom:1px solid #f1f3f5}.era-section:last-child{border-bottom:none}.era-header{width:100%;padding:.75rem 1.5rem;font-size:.95rem;font-weight:500;text-align:left;color:#495057;background-color:#fafbfc;border:none;cursor:pointer;display:flex;justify-content:space-between;align-items:center;transition:background-color .15s ease-in-out}.era-header:hover{background-color:#f1f3f5}.era-header span:first-child{font-size:1.6rem;font-weight:500}.era-arrow{font-size:1rem;color:#6c757d;transition:transform .2s ease;display:inline-block}.era-arrow.open{transform:rotate(90deg)}.lesson-list{list-style:none;padding:0;margin:0}.lesson-list li{border-bottom:1px solid #f8f9fa}.lesson-list li:last-child{border-bottom:none}.lesson-list a{display:flex;align-items:center;padding:.75rem 2rem;color:#495057;text-decoration:none;border-left:3px solid transparent;transition:all .15s ease-in-out}.lesson-list a:hover{background-color:#f8f9fa;color:#212529}.lesson-list a.active{background-color:var(--active-bg,#e7f3ff);color:var(--active-text,#0056b3);font-weight:500;border-left:3px solid var(--active-border,#0056b3)}.lesson-list .lesson-no{min-width:3rem;padding:.25rem .5rem;font-weight:600;color:#6c757d;background-color:#f1f3f5;border-radius:.25rem;margin-right:.75rem;text-align:center}.lesson-list a.active .lesson-no{background-color:var(--active-text,#0056b3);color:#fff}.lesson-list .lesson-title{flex:1;font-size:1.6rem;line-height:1.5}.accordion-content{animation:slideDown .2s ease-out}@keyframes slideDown{0%{opacity:0;max-height:0}to{opacity:1;max-height:2000px}}