* { font-family: 'Inter', sans-serif; }
        .scrollbar-thin::-webkit-scrollbar { width: 6px; }
        .scrollbar-thin::-webkit-scrollbar-track { background: #f1f5f9; }
        .scrollbar-thin::-webkit-scrollbar-thumb { background: #cbd5e0; border-radius: 3px; }
        .scrollbar-thin::-webkit-scrollbar-thumb:hover { background: #a0aec0; }
        .module-content { max-height: 0; overflow: hidden; transition: max-height 0.3s ease-out; }
        .module-content.expanded { max-height: 2000px; }
        .lesson-btn { transition: all 0.2s; }
        .lesson-btn:hover { background-color: #f8fafc; }
        .lesson-btn.active { background-color: #eff6ff; color: #2563eb; border-left: 3px solid #2563eb; }
        .lesson-btn.completed .lesson-icon { background-color: #dcfce7; color: #16a34a; }
        .lesson-btn.current .lesson-icon { background-color: #dbeafe; color: #2563eb; }
        .lesson-btn.locked .lesson-icon { background-color: #f1f5f9; color: #94a3b8; }
        .slide-img { max-width: 100%; height: auto; display: block; }