/* Responsive Styles */
@media (max-width: 768px) {
    .nav-content {
        padding: 1rem;
    }
    
    .nav-links {
        display: none;
    }
    
    .main {
        padding: 1rem;
    }
    
    .hero {
        padding: 2rem 0 1.5rem;
    }
    
    .hero-title {
        font-size: 2rem;
    }
    
    .subject-header {
        padding: 1rem;
    }
    
    .topic-group {
        padding: 0 1rem 1rem;
    }
    
    .material-card {
        padding: 0.75rem;
    }
    
    .material-name {
        font-size: 0.875rem;
    }
    
    /* PDF Viewer Responsive */
    .pdf-section-header {
        flex-direction: column;
        align-items: flex-start;
        gap: 1rem;
    }
    
    .pdf-selector {
        overflow-x: auto;
        flex-wrap: nowrap;
        padding-bottom: 0.5rem;
        -webkit-overflow-scrolling: touch;
    }
    
    .pdf-tab {
        white-space: nowrap;
        flex-shrink: 0;
    }
    
    .pdf-embed-wrapper {
        height: 500px;
    }
    
    .pdf-viewer-header {
        flex-direction: column;
        gap: 1rem;
        align-items: flex-start;
    }
    
    .pdf-actions {
        width: 100%;
    }
    
    .pdf-action-btn {
        flex: 1;
        justify-content: center;
    }
}

@media (max-width: 480px) {
    .pdf-embed-wrapper {
        height: 400px;
    }
}