:root {
            --primary: #1e293b;
            --primary-light: #334155;
            --accent: #10b981;
            --accent-dark: #059669;
            --text-primary: #0f172a;
            --text-secondary: #64748b;
            --text-light: #94a3b8;
            --bg-main: #ffffff;
            --bg-secondary: #f8fafc;
            --border: #e2e8f0;
            --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
            --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
            --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
            --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
        }

        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', sans-serif;
            line-height: 1.6;
            color: var(--text-primary);
            background: var(--bg-secondary);
            -webkit-font-smoothing: antialiased;
        }

        /* Header */
        header {
            background: var(--bg-main);
            border-bottom: 1px solid var(--border);
            padding: 2.5rem 0;
        }

        .header-content {
            max-width: 1280px;
            margin: 0 auto;
            padding: 0 2rem;
        }

        header h1 {
            font-size: 2rem;
            font-weight: 600;
            color: var(--text-primary);
            margin-bottom: 0.5rem;
            letter-spacing: -0.025em;
        }

        header p {
            font-size: 1rem;
            color: var(--text-secondary);
            font-weight: 400;
        }

        /* Navigation */
        nav {
            background: var(--bg-main);
            border-bottom: 1px solid var(--border);
            position: sticky;
            top: 0;
            z-index: 100;
        }

        nav ul {
            list-style: none;
            display: flex;
            max-width: 1280px;
            margin: 0 auto;
            padding: 0 2rem;
        }

        nav a {
            display: block;
            padding: 1rem 1.5rem;
            text-decoration: none;
            color: var(--text-secondary);
            font-weight: 500;
            font-size: 0.9375rem;
            transition: color 0.2s;
            border-bottom: 2px solid transparent;
        }

        nav a:hover {
            color: var(--text-primary);
        }

        nav a.active {
            color: var(--accent);
            border-bottom-color: var(--accent);
        }

        /* Main Container */
        .container {
            max-width: 1280px;
            margin: 0 auto;
            padding: 3rem 2rem;
        }

        /* Section */
        section {
            display: none;
        }

        section.active {
            display: block;
            animation: fadeIn 0.3s ease-in-out;
        }

        @keyframes fadeIn {
            from { opacity: 0; }
            to { opacity: 1; }
        }

        h2 {
            font-size: 1.875rem;
            font-weight: 600;
            color: var(--text-primary);
            margin-bottom: 2rem;
            letter-spacing: -0.025em;
        }

        /* Search Bar */
        .search-container {
            margin-bottom: 2rem;
            width: 100%;
        }

        .search-box {
            display: flex;
            align-items: center;
            background: #f3f4f6;
            border: 1px solid #e5e7eb;
            border-radius: 12px;
            padding: 0 16px;
        }

        .search-box input {
            flex: 1;
            border: none;
            background: transparent;
            padding: 14px 0;
            font-size: 15px;
            outline: none;
        }

        .search-box input::placeholder {
            color: #9ca3af;
        }

        .divider {
    width: 1px;
    height: 24px;
    background: #d1d5db;
    margin: 0 16px;
}

        /* .search-box input:focus {
            outline: none;
            border-color: var(--accent);
            box-shadow: 0 0 0 3px rgba(16, 185, 129, 0.1);
        } */

        .search-icon {
            color: #9ca3af;
            margin-right: 10px;
        }

        .search-box input::placeholder {
            color: var(--text-light);
        }

        /* Grid */
        .books-grid,
        .phds-grid,
        .lectures-grid {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
            gap: 1.5rem;
        }

        /* Card */
        .book-card,
        .phd-card,
        .lecture-card {
            background: var(--bg-main);
            border: 1px solid var(--border);
            border-radius: 12px;
            overflow: hidden;
            transition: all 0.2s;
            display: flex;
            flex-direction: column;
        }

        .book-card:hover,
        .phd-card:hover,
        .lecture-card:hover {
            box-shadow: var(--shadow-lg);
            border-color: var(--accent);
            transform: translateY(-4px);
        }

        .phd-card {
            cursor: pointer;
        }

        /* Book/Lecture/PhD Cover */
        .book-cover,
        .phd-thumbnail,
        .lecture-thumbnail {
            aspect-ratio: 16/10;
            background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%);
            display: flex;
            align-items: center;
            justify-content: center;
            padding: 0;
            position: relative;
            overflow: hidden;
            background-size: contain;
            background-position: center;
            background-repeat: no-repeat;
        }

        .lecture-thumbnail {
            background: linear-gradient(135deg, #1e293b 0%, #334155 100%);
            cursor: pointer;
            padding: 2rem;
        }

        .book-cover-text,
        .phd-thumbnail-text {
            font-size: 1.125rem;
            font-weight: 600;
            color: white;
            text-align: center;
            line-height: 1.4;
            position: relative;
            z-index: 1;
            text-shadow: 0 2px 4px rgba(0,0,0,0.3);
            display: none;
        }

        .book-cover:not([style*="background-image"]) .book-cover-text,
        .phd-thumbnail:not([style*="background-image"]) .phd-thumbnail-text {
            display: block;
        }


        .play-icon {
            width: 64px;
            height: 64px;
            background: rgba(255, 255, 255, 0.95);
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 1.5rem;
            color: var(--primary);
            transition: all 0.2s;
        }

        .lecture-card:hover .play-icon {
            transform: scale(1.1);
            background: var(--accent);
            color: white;
        }

        /* Card Content */
        .book-info,
        .lecture-info,
        .phd-info {
            padding: 1.5rem;
            flex: 1;
            display: flex;
            flex-direction: column;
        }

        .book-title,
        .lecture-title,
        .phd-title {
            font-size: 1.125rem;
            font-weight: 600;
            color: var(--text-primary);
            margin-bottom: 0.5rem;
            line-height: 1.4;
        }

        .phd-subtitle {
            font-size: 0.9rem;
            color: var(--text-secondary);
            margin-bottom: 0.5rem;
        }

        .book-description,
        .lecture-description,
        .phd-description {
            font-size: 0.875rem;
            color: var(--text-secondary);
            margin-bottom: 1rem;
            line-height: 1.6;
            flex: 1;
        }

        /* Notice */

        .notice {
            display: flex;
            align-items: center;
            gap: 0.75rem;
            padding: 0.9rem 1.25rem;
            margin: 1rem 2rem 0;
            border-radius: 8px;
            background: rgba(59, 130, 246, 0.08); /* soft blue */
            border: 1px solid rgba(59, 130, 246, 0.25);
            color: #1e3a8a;
            font-size: 0.95rem;
            font-weight: 500;
        }

        .notice-icon {
            font-size: 1.1rem;
            line-height: 1;
        }

        /* CV button */

        .cv-btn {
            margin-top: 2rem;
            display: inline-block;
            padding: 0.45rem 1.1rem;
            font-size: 0.75rem;
            font-weight: 500;
            color: #ffffff;
            text-decoration: none;
            border: 1px solid rgba(255, 255, 255, 0.6);
            border-radius: 4px;
            background: transparent;
            transition: all 0.2s ease;
        }

        .cv-btn:hover {
            background: rgba(255, 255, 255, 0.12);
        }



        /* Meta Info */
        .book-meta,
        .lecture-meta,
        .gallery-modal-meta {
            display: flex;
            gap: 1rem;
            margin-bottom: 1rem;
            flex-wrap: wrap;
        }

        .phd-meta {
            display: flex;
            gap: 1rem;
            margin-bottom: 1rem;
            flex-wrap: wrap;
            justify-content: flex-end;
        }

        .gallery-meta{
            display: flex;
            gap: 0rem;
            margin-bottom: 0.5rem;
            flex-wrap: wrap;
        }

        .book-meta span,
        .lecture-meta span,
        .gallery-meta span,
        .gallery-modal-meta span {
            font-size: 0.8125rem;
            color: var(--text-light);
            display: flex;
            align-items: center;
            gap: 0.375rem;
        }

        .phd-meta span {
            font-size: 0.8125rem;
            color: var(--text-light);
            display: flex;
            align-items: center;
            gap: 0.375rem;
        }

        /* Buttons */
        .book-actions,
        .lecture-actions {
            display: flex;
            gap: 0.75rem;
        }

        .btn {
            flex: 1;
            padding: 0.625rem 1rem;
            border: none;
            border-radius: 6px;
            cursor: pointer;
            font-weight: 500;
            font-size: 0.875rem;
            transition: all 0.2s;
            text-align: center;
            font-family: inherit;
        }

        .btn-primary {
            background: var(--accent);
            color: white;
        }

        .btn-primary:hover {
            background: var(--accent-dark);
        }

        .btn-secondary {
            background: transparent;
            color: var(--text-secondary);
            border: 1px solid var(--border);
        }

        .btn-secondary:hover {
            background: var(--bg-secondary);
            border-color: var(--text-secondary);
            color: var(--text-primary);
        }

        /* Modal */
        .modal {
            display: none;
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background: rgba(15, 23, 42, 0.7);
            backdrop-filter: blur(4px);
            z-index: 1000;
            padding: 1rem;
        }

        .modal.active {
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .modal-content {
            background: var(--bg-main);
            border-radius: 12px;
            max-width: 1200px;
            width: 100%;
            height: 90vh;           
            overflow: hidden;
            display: flex;
            flex-direction: column;
            box-shadow: var(--shadow-lg);
        }

        .modal-header {
            padding: 1rem 1.5rem;
            border-bottom: 1px solid var(--border);
            display: flex;
            justify-content: space-between;
            align-items: center;
            flex: 0 0 auto;
        }

        .modal-header h3 {
            font-size: 1.125rem;
            font-weight: 600;
            color: var(--text-primary);
        }

        .close-btn {
            background: transparent;
            border: none;
            color: var(--text-secondary);
            font-size: 1.5rem;
            cursor: pointer;
            width: 32px;
            height: 32px;
            border-radius: 6px;
            display: flex;
            align-items: center;
            justify-content: center;
            transition: all 0.2s;
        }

        .close-btn:hover {
            background: var(--bg-secondary);
            color: var(--text-primary);
        }

        .modal-body {
            padding: 0;               
            overflow-y: auto;
            flex: 1;
        }

        /* PDF.js Viewer Styles */
        #pdf-reader {
            width: 100%;
            height: 100%;
            display: flex;
            flex-direction: column;
            background: #f8f9fa;
        }

        #pdf-controls {
            background: var(--bg-main);
            border-bottom: 1px solid var(--border);
            padding: 1rem 1.5rem;
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 1rem;
            flex-wrap: wrap;
        }

        .control-group {
            display: flex;
            align-items: center;
            gap: 0.75rem;
        }

        .control-btn {
            background: var(--bg-secondary);
            border: 1px solid var(--border);
            padding: 0.5rem 0.75rem;
            border-radius: 6px;
            cursor: pointer;
            font-size: 0.875rem;
            color: var(--text-primary);
            transition: all 0.2s;
            font-family: inherit;
            display: flex;
            align-items: center;
            gap: 0.5rem;
        }

        .control-btn:hover:not(:disabled) {
            background: var(--bg-main);
            border-color: var(--accent);
        }

        .control-btn:disabled {
            opacity: 0.5;
            cursor: not-allowed;
        }

        .control-btn svg {
            flex-shrink: 0;
        }

        .page-info {
            font-size: 0.875rem;
            color: var(--text-secondary);
            display: flex;
            align-items: center;
            gap: 0.5rem;
        }

        #page-input {
            width: 50px;
            padding: 0.375rem;
            border: 1px solid var(--border);
            border-radius: 4px;
            text-align: center;
            font-size: 0.875rem;
        }

        #zoom-select {
            padding: 0.5rem 0.75rem;
            border: 1px solid var(--border);
            border-radius: 6px;
            font-size: 0.875rem;
            background: var(--bg-main);
            color: var(--text-primary);
            cursor: pointer;
            min-width: 80px;
        }

        #pdf-canvas-container {
            flex: 1;
            overflow-y: auto;
            padding: 2rem;
            display: flex;
            flex-direction: column;
            align-items: center;
            gap: 1.5rem;
            opacity: 0;
            transition: opacity 0.3s ease-in-out;
        }

        #pdf-canvas-container.loaded {
            opacity: 1;
        }

        .pdf-page {
            background: white;
            box-shadow: var(--shadow-md);
            border-radius: 4px;
            margin-bottom: 1rem;
        }

        #pdf-loading {
            display: none;
            text-align: center;
            padding: 3rem;
            color: var(--text-secondary);
        }

        .spinner {
            width: 40px;
            height: 40px;
            border: 3px solid var(--border);
            border-top-color: var(--accent);
            border-radius: 50%;
            animation: spin 1s linear infinite;
            margin: 0 auto 1rem;
        }

        @keyframes spin {
            to { transform: rotate(360deg); }
        }

        /* Fullscreen styles */
        .modal-content:fullscreen {
            max-width: 100%;
            max-height: 100%;
            width: 100%;
            height: 100%;
            border-radius: 0;
        }

        .modal-content:-webkit-full-screen {
            max-width: 100%;
            max-height: 100%;
            width: 100%;
            height: 100%;
            border-radius: 0;
        }

        .modal-content:-moz-full-screen {
            max-width: 100%;
            max-height: 100%;
            width: 100%;
            height: 100%;
            border-radius: 0;
        }

        .modal-content:-ms-fullscreen {
            max-width: 100%;
            max-height: 100%;
            width: 100%;
            height: 100%;
            border-radius: 0;
        }

        /* PDF Viewer & Video */
        #pdfViewer {
            width: 100%;
            height: 100%;
            border: none;
            border-radius: 8px;
        }

        .video-container {
            position: relative;
            width: 100%;
            padding-bottom: 56.25%;
            height: 0;
            overflow: hidden;
            border-radius: 8px;
            background: #000;
        }

        .video-container iframe {
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            border: none;
        }

        /* YouTube Player Container */
        #youtube-player-container {
            width: 100%;
            height: 100%;
            background: #000;
            display: flex;
            flex-direction: column;
        }

        #youtube-player {
            flex: 1;
            width: 100%;
            background: #000;
        }

        /* Custom Video Controls */
        .video-controls {
            background: linear-gradient(to top, rgba(0,0,0,0.9) 0%, rgba(0,0,0,0.7) 70%, transparent 100%);
            padding: 1rem 1.5rem;
            display: flex;
            flex-direction: column;
            gap: 0.75rem;
            position: absolute;
            bottom: 0;
            left: 0;
            right: 0;
            transition: opacity 0.3s;
        }

        .video-controls.hidden {
            opacity: 0;
            pointer-events: none;
        }

        .progress-container {
            width: 100%;
            height: 5px;
            background: rgba(255,255,255,0.3);
            border-radius: 3px;
            cursor: pointer;
            position: relative;
        }

        .progress-bar {
            height: 100%;
            background: var(--accent);
            border-radius: 3px;
            width: 0%;
            transition: width 0.1s;
        }

        .progress-handle {
            position: absolute;
            top: 50%;
            transform: translate(-50%, -50%);
            width: 14px;
            height: 14px;
            background: white;
            border-radius: 50%;
            box-shadow: 0 2px 4px rgba(0,0,0,0.3);
            opacity: 0;
            transition: opacity 0.2s;
        }

        .progress-container:hover .progress-handle {
            opacity: 1;
        }

        .controls-row {
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 1rem;
        }

        .controls-left,
        .controls-right {
            display: flex;
            align-items: center;
            gap: 0.75rem;
        }

        .video-btn {
            background: transparent;
            border: none;
            color: white;
            cursor: pointer;
            padding: 0.5rem;
            display: flex;
            align-items: center;
            justify-content: center;
            transition: all 0.2s;
            border-radius: 4px;
        }

        .video-btn:hover {
            background: rgba(255,255,255,0.1);
        }

        .video-btn svg {
            width: 24px;
            height: 24px;
        }

        .time-display {
            color: white;
            font-size: 0.875rem;
            font-weight: 500;
            min-width: 100px;
        }

        .speed-control {
            position: relative;
        }

        .speed-btn {
            background: rgba(255,255,255,0.1);
            border: 1px solid rgba(255,255,255,0.3);
            color: white;
            padding: 0.4rem 0.75rem;
            border-radius: 4px;
            cursor: pointer;
            font-size: 0.875rem;
            font-weight: 500;
            transition: all 0.2s;
        }

        .speed-btn:hover {
            background: rgba(255,255,255,0.2);
        }

        .speed-menu {
            position: absolute;
            bottom: 100%;
            right: 0;
            background: rgba(28, 28, 28, 0.95);
            backdrop-filter: blur(10px);
            border-radius: 8px;
            padding: 0.5rem;
            margin-bottom: 0.5rem;
            display: none;
            flex-direction: column;
            gap: 0.25rem;
            min-width: 80px;
            box-shadow: 0 4px 12px rgba(0,0,0,0.3);
        }

        .speed-menu.active {
            display: flex;
        }

        .speed-option {
            background: transparent;
            border: none;
            color: white;
            padding: 0.5rem 0.75rem;
            cursor: pointer;
            text-align: left;
            font-size: 0.875rem;
            border-radius: 4px;
            transition: background 0.2s;
        }

        .speed-option:hover {
            background: rgba(255,255,255,0.1);
        }

        .speed-option.active {
            color: var(--accent);
            font-weight: 600;
        }

        .volume-control {
            display: flex;
            align-items: center;
            gap: 0.5rem;
        }

        .volume-slider {
            width: 80px;
            height: 4px;
            background: rgba(255,255,255,0.3);
            border-radius: 2px;
            position: relative;
            cursor: pointer;
        }

        .volume-bar {
            height: 100%;
            background: white;
            border-radius: 2px;
            width: 100%;
        }

        /* Order Form */
        .order-form {
            max-width: 600px;
        }

        .form-group {
            margin-bottom: 1.25rem;
        }

        .form-group label {
            display: block;
            margin-bottom: 0.5rem;
            font-weight: 500;
            font-size: 0.875rem;
            color: var(--text-primary);
        }

        .form-group input,
        .form-group textarea {
            width: 100%;
            padding: 0.625rem 0.75rem;
            border: 1px solid var(--border);
            border-radius: 6px;
            font-family: inherit;
            font-size: 0.9375rem;
            transition: all 0.2s;
            color: var(--text-primary);
            background: var(--bg-main);
        }

        .form-group textarea {
            resize: vertical;
            min-height: 100px;
        }

        .form-group input:focus,
        .form-group textarea:focus {
            outline: none;
            border-color: var(--accent);
            box-shadow: 0 0 0 3px rgba(16, 185, 129, 0.1);
        }

        /* Success Message */
        .success-message {
            background: #d1fae5;
            color: #065f46;
            padding: 1rem;
            border-radius: 8px;
            margin-bottom: 1rem;
            border: 1px solid #6ee7b7;
            font-size: 0.9375rem;
        }

        /* No Results */
        .no-results {
            text-align: center;
            padding: 4rem 2rem;
            background: var(--bg-main);
            border: 1px solid var(--border);
            border-radius: 12px;
        }

        .no-results-icon {
            font-size: 3rem;
            margin-bottom: 1rem;
            opacity: 0.3;
        }

        .no-results-text {
            font-size: 1rem;
            color: var(--text-secondary);
        }

        /* About Section */
                .about-content {
            background: var(--bg-main);
            padding: 0;
            border-radius: 12px;
            border: 1px solid var(--border);

            max-width: 100%;     /* 🔥 remove width limit */
            width: 100%;
            margin: 0 auto;     /* keeps it centered */
        }


        .about-header {
            background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%);
            color: white;
            padding: 2.5rem;
            border-radius: 12px 12px 0 0;
        }

        .about-header h3 {
            font-size: 1.75rem;
            font-weight: 600;
            margin-bottom: 0.5rem;
            letter-spacing: -0.025em;
        }

        .about-header p {
            font-size: 1rem;
            opacity: 0.9;
            margin: 0;
        }

        .about-body {
            padding: 2.5rem;
        }

        .about-section {
            margin-bottom: 2.5rem;
        }

        .about-section:last-child {
            margin-bottom: 0;
        }

        .about-section h4 {
            font-size: 1.25rem;
            font-weight: 600;
            color: var(--text-primary);
            margin-bottom: 1rem;
            display: flex;
            align-items: center;
            gap: 0.5rem;
        }

        .about-section h4::before {
            content: '';
            width: 4px;
            height: 1.25rem;
            background: var(--accent);
            border-radius: 2px;
        }

        .about-section p {
            font-size: 1rem;
            line-height: 1.8;
            color: var(--text-secondary);
            margin-bottom: 1rem;
        }

        .about-section ul {
            list-style: none;
            padding: 0;
            margin: 1rem 0;
        }

        .about-section ul li {
            font-size: 0.9375rem;
            line-height: 1.7;
            color: var(--text-secondary);
            padding: 0.5rem 0;
            padding-left: 1.5rem;
            position: relative;
        }

        .about-section ul li::before {
            content: '•';
            color: var(--accent);
            font-weight: bold;
            position: absolute;
            left: 0.5rem;
        }

        .stats-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
            gap: 1.5rem;
            margin: 1.5rem 0;
        }

        .stat-card {
            background: var(--bg-secondary);
            padding: 1.5rem;
            border-radius: 8px;
            border: 1px solid var(--border);
            text-align: center;
        }

        .stat-number {
            font-size: 2rem;
            font-weight: 700;
            color: var(--accent);
            margin-bottom: 0.5rem;
        }

        .stat-label {
            font-size: 0.875rem;
            color: var(--text-secondary);
            font-weight: 500;
        }

        .highlight-box {
            background: var(--bg-secondary);
            border-left: 4px solid var(--accent);
            padding: 1.5rem;
            border-radius: 0 8px 8px 0;
            margin: 1.5rem 0;
        }

        .highlight-box p {
            margin: 0;
            font-size: 0.9375rem;
            line-height: 1.7;
        }

        .specializations {
            display: flex;
            flex-wrap: wrap;
            gap: 0.75rem;
            margin: 1rem 0;
        }

        .specialization-tag {
            background: var(--bg-secondary);
            color: var(--accent);
            padding: 0.5rem 1rem;
            border-radius: 20px;
            font-size: 0.875rem;
            font-weight: 500;
            border: 1px solid var(--border);
        }

        .contact-details {
            background: var(--bg-secondary);
            padding: 1.5rem;
            border-radius: 8px;
            border: 1px solid var(--border);
        }

        .contact-details p {
            margin: 0.5rem 0;
            font-size: 0.95rem;
            color: var(--text-secondary);
        }

        .contact-details a {
            color: var(--accent);
            text-decoration: none;
            font-weight: 500;
        }

        .contact-details a:hover {
            text-decoration: underline;
        }


        /* Responsive */
        @media (max-width: 768px) {
            header h1 {
                font-size: 1.5rem;
            }

            header p {
                font-size: 0.9375rem;
            }

            nav ul {
                padding: 0 1rem;
            }

            nav a {
                padding: 0.875rem 1rem;
                font-size: 0.875rem;
            }

            .container {
                padding: 2rem 1rem;
            }

            h2 {
                font-size: 1.5rem;
            }

            .books-grid,
            .lectures-grid {
                grid-template-columns: 1fr;
                gap: 1rem;
            }

            .book-actions,
            .lecture-actions {
                flex-direction: column;
            }

            .modal-content {
                max-width: 95%;
                max-height: 95vh;
            }

            .modal-header {
                padding: 1rem;
            }

            .modal-body {
                padding: 1rem;
            }

            #pdfViewer {
                height: 60vh;
            }
        }

   .sort-wrapper {
    display: flex;
    align-items: center;
    justify-content: flex-end;
    gap: 12px;
    margin: 0 0 24px auto;
    max-width: 320px;
}


.sort-wrapper label {
    font-weight: 500;
    color: #555;
}

.sort-wrapper select {
    appearance: none;
    -webkit-appearance: none;
    -moz-appearance: none;

    padding: 8px 36px 8px 12px;
    border-radius: 8px;
    border: 1px solid #ddd;
    background-color: #fff;

    font-size: 12px;
    cursor: pointer;
    transition: all 0.2s ease;

    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='14' height='14' viewBox='0 0 24 24' fill='none' stroke='%23666' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
}

.sort-wrapper select:hover {
    border-color: #bbb;
}

.sort-wrapper select:focus {
    outline: none;
    border-color: #2b6cb0;
    box-shadow: 0 0 0 2px rgba(43, 108, 176, 0.15);
}

/* Sort Section */
.sort-section {
    display: flex;
    align-items: center;
    gap: 8px;
}

.sort-section span {
    font-size: 12px;
    font-weight: 600;
    color: #6b7280;
    letter-spacing: 0.5px;
}

.sort-section select {
    border: none;
    background: transparent;
    font-size: 12px;
    cursor: pointer;
    outline: none;
}

.lecture-thumbnail {
    background-size: cover;
    background-position: center;
}

.lecture-thumbnail::after {
    content: "";
    position: absolute;
    inset: 0;
    background: rgba(0, 0, 0, 0.25);
    opacity: 0;
    transition: opacity 0.2s ease;
}

.lecture-thumbnail:hover::after {
    opacity: 1;
}

/* Gallery Section */
        .gallery-grid {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
            gap: 2rem;
            margin-top: 2rem;
        }

        .gallery-item {
            background: var(--bg-main);
            border: 1px solid var(--border);
            border-radius: 12px;
            overflow: hidden;
            transition: all 0.3s;
            cursor: pointer;
        }

        .gallery-item:hover {
            transform: translateY(-4px);
            box-shadow: var(--shadow-lg);
            border-color: var(--accent);
        }

        .gallery-image {
            width: 100%;
            height: 220px;
            background-size: cover;
            background-position: center;
            border-radius: 8px 8px 0 0;
        }

        .gallery-info {
            padding: 1.5rem;
        }

        .gallery-title {
            font-size: 1.125rem;
            font-weight: 600;
            color: var(--text-primary);
            margin-bottom: 0.75rem;
            line-height: 1.4;
        }

        .gallery-description {
            font-size: 0.9375rem;
            color: var(--text-secondary);
            line-height: 1.6;
        }

        /* Gallery Modal */
        .gallery-modal {
            display: none;
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background: rgba(0, 0, 0, 0.95);
            z-index: 2000;
            overflow-y: auto;
            padding: 2rem;
        }

        .gallery-modal.active {
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .gallery-modal-content {
            max-width: 900px;
            width: 100%;
            margin: auto;
            position: relative;
            display: flex;
            flex-direction: column;
            gap: 0;
        }

        .gallery-modal-image {
            width: 100%;
            max-height: 70vh;
            object-fit: contain;
            display: block;
            border-radius: 0;
        }

        .gallery-modal-info {
            background: white;
            padding: 1.5rem 2rem;
            border-radius: 0;
            margin-top: 0;
        }

        .gallery-modal-title {
            font-size: 1.25rem;
            font-weight: 600;
            color: #1e293b;
            margin-bottom: 0.75rem;
        }

        .gallery-modal-description {
            font-size: 0.95rem;
            color: #64748b;
            line-height: 1.6;
        }

        .gallery-modal-close {
            position: fixed;
            top: 1.5rem;
            right: 1.5rem;
            background: white;
            border: none;
            width: 40px;
            height: 40px;
            border-radius: 50%;
            font-size: 1.5rem;
            cursor: pointer;
            display: flex;
            align-items: center;
            justify-content: center;
            transition: all 0.2s;
            z-index: 2001;
            box-shadow: 0 2px 8px rgba(0,0,0,0.2);
            color: #1e293b;
        }

        .gallery-modal-close:hover {
            background: #ef4444;
            color: white;
            transform: scale(1.05);
        }

        @media (max-width: 768px) {
            .gallery-modal {
                padding: 1rem;
            }
            
            .gallery-modal-content {
                max-width: 100%;
            }
            
            .gallery-modal-image {
                max-height: 50vh;
            }
            
            .gallery-modal-info {
                padding: 1rem 1.25rem;
            }
            
            .gallery-modal-title {
                font-size: 1.1rem;
            }
            
            .gallery-modal-description {
                font-size: 0.9rem;
            }
            
            .gallery-modal-close {
                top: 1rem;
                right: 1rem;
                width: 36px;
                height: 36px;
                font-size: 1.25rem;
            }
        }
        

        @media (max-width: 480px) {
            header {
                padding: 1.5rem 0;
            }

            header h1 {
                font-size: 1.25rem;
            }

            nav a {
                padding: 0.75rem 0.75rem;
            }

            .container {
                padding: 1.5rem 1rem;
            }

            h2 {
                font-size: 1.25rem;
                margin-bottom: 1.5rem;
            }

            .divider{
                display: none;
            }

            .sort-section select {
    background: transparent;
    border: none;
    font-size: 12px;
}



            .search-container {
                width: 100%;
                margin-bottom: 2rem;
            }
        }