:root {
            --primary-color: #4a6fa5;
            --secondary-color: #166088;
            --accent-color: #4fc3f7;
            --light-color: #f8f9fa;
            --dark-color: #343a40;
            --success-color: #28a745;
            --warning-color: #ffc107;
            --danger-color: #dc3545;
            --whatsapp-color: #25D366;
            --border-radius: 5px;
            --box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
        }

        /* Dark mode variables */
        [data-theme="dark"] {
            --primary-color: #5d8acd;
            --secondary-color: #1a73e8;
            --accent-color: #4fc3f7;
            --light-color: #343a40;
            --dark-color: #f8f9fa;
            --success-color: #28a745;
            --warning-color: #ffc107;
            --danger-color: #dc3545;
            --whatsapp-color: #25D366;
            --box-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
        }

        * {
            box-sizing: border-box;
            margin: 0;
            padding: 0;
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            transition: background-color 0.3s, color 0.3s;
        }

        body {
            background-color: #f5f7fa;
            color: var(--dark-color);
            line-height: 1.6;
            padding: 20px;
        }

        [data-theme="dark"] body {
            background-color: #212529;
        }

        .container {
            max-width: 1000px;
            margin: 0 auto;
            padding: 20px;
            background-color: white;
            border-radius: var(--border-radius);
            box-shadow: var(--box-shadow);
        }

        [data-theme="dark"] .container {
            background-color: #2c3034;
        }

        header {
            text-align: center;
            margin-bottom: 30px;
            padding-bottom: 20px;
            border-bottom: 1px solid #eee;
        }

        [data-theme="dark"] header {
            border-bottom-color: #444;
        }

        h1 {
            color: var(--secondary-color);
            margin-bottom: 10px;
        }

        h2 {
            color: var(--secondary-color);
            margin-bottom: 15px;
            padding-bottom: 10px;
            border-bottom: 1px solid #eee;
        }

        [data-theme="dark"] h2 {
            border-bottom-color: #444;
        }

        .app-description {
            color: #666;
            font-size: 16px;
        }

        [data-theme="dark"] .app-description {
            color: #aaa;
        }

        .app-controls {
            display: flex;
            flex-wrap: wrap;
            gap: 15px;
            margin-bottom: 20px;
            padding: 15px;
            background-color: #f8f9fa;
            border-radius: var(--border-radius);
        }

        [data-theme="dark"] .app-controls {
            background-color: #343a40;
        }

        .input-group {
            flex: 1;
            min-width: 200px;
        }

        label {
            display: block;
            margin-bottom: 5px;
            font-weight: 600;
            color: var(--secondary-color);
        }

        input, select, textarea {
            width: 100%;
            padding: 10px;
            border: 1px solid #ddd;
            border-radius: var(--border-radius);
            font-size: 16px;
            background-color: white;
            color: #333;
        }

        [data-theme="dark"] input,
        [data-theme="dark"] select,
        [data-theme="dark"] textarea {
            background-color: #3a3f44;
            border-color: #444;
            color: #eee;
        }

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

        input:focus, select:focus, textarea:focus {
            outline: none;
            border-color: var(--accent-color);
            box-shadow: 0 0 0 2px rgba(79, 195, 247, 0.2);
        }

        button {
            padding: 10px 15px;
            border: none;
            border-radius: var(--border-radius);
            background-color: var(--primary-color);
            color: white;
            font-size: 16px;
            cursor: pointer;
            transition: all 0.3s ease;
        }

        button:hover {
            background-color: var(--secondary-color);
            transform: translateY(-1px);
        }

        button:active {
            transform: translateY(0);
        }

        button.add-btn {
            background-color: var(--success-color);
            align-self: flex-end;
        }

        button.add-btn:hover {
            background-color: #218838;
        }

        button.edit-btn {
            background-color: var(--warning-color);
            color: var(--dark-color);
        }

        button.edit-btn:hover {
            background-color: #e0a800;
        }

        button.delete-btn {
            background-color: var(--danger-color);
        }

        button.delete-btn:hover {
            background-color: #c82333;
        }

        button.complete-btn {
            background-color: var(--success-color);
        }

        button.complete-btn:hover {
            background-color: #218838;
        }

        button.filter-btn {
            background-color: #6c757d;
        }

        button.filter-btn:hover {
            background-color: #5a6268;
        }

        button.active-filter {
            background-color: var(--secondary-color);
        }

        button.whatsapp-btn {
            background-color: var(--whatsapp-color);
        }

        button.whatsapp-btn:hover {
            background-color: #128C7E;
        }

        button.export-btn {
            background-color: #6f42c1;
        }

        button.export-btn:hover {
            background-color: #5a32a3;
        }

        button.email-btn {
            background-color: #d63384;
        }

        button.email-btn:hover {
            background-color: #b02a6f;
        }

        button.clear-btn {
            background-color: #fd7e14;
        }

        button.clear-btn:hover {
            background-color: #dc6e10;
        }

        .task-list {
            margin-bottom: 30px;
        }

        .task-item {
            display: flex;
            flex-wrap: wrap;
            align-items: center;
            padding: 15px;
            margin-bottom: 10px;
            background-color: white;
            border-radius: var(--border-radius);
            box-shadow: var(--box-shadow);
            transition: all 0.3s ease;
            border-left: 4px solid transparent;
        }

        [data-theme="dark"] .task-item {
            background-color: #3a3f44;
        }

        .task-item:hover {
            transform: translateY(-2px);
            box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
        }

        [data-theme="dark"] .task-item:hover {
            box-shadow: 0 4px 15px rgba(0, 0, 0, 0.3);
        }

        .task-item.completed {
            background-color: #f8f9fa;
            border-left-color: var(--success-color);
        }

        [data-theme="dark"] .task-item.completed {
            background-color: #2a2e32;
        }

        .task-item.high-priority {
            border-left-color: var(--danger-color);
        }

        .task-item.medium-priority {
            border-left-color: var(--warning-color);
        }

        .task-content {
            flex: 1;
            min-width: 250px;
            margin-right: 15px;
        }

        .task-title {
            font-weight: 600;
            margin-bottom: 5px;
            word-break: break-word;
        }

        .task-description {
            color: #666;
            font-size: 14px;
            margin-bottom: 5px;
            word-break: break-word;
        }

        [data-theme="dark"] .task-description {
            color: #aaa;
        }

        .task-meta {
            display: flex;
            flex-wrap: wrap;
            gap: 10px;
            font-size: 13px;
            color: #888;
        }

        [data-theme="dark"] .task-meta {
            color: #aaa;
        }

        .task-priority {
            padding: 2px 8px;
            border-radius: 10px;
            font-size: 12px;
            font-weight: 600;
        }

        .priority-high {
            background-color: #f8d7da;
            color: var(--danger-color);
        }

        [data-theme="dark"] .priority-high {
            background-color: #4a2528;
        }

        .priority-medium {
            background-color: #fff3cd;
            color: #856404;
        }

        [data-theme="dark"] .priority-medium {
            background-color: #4a3f13;
        }

        .priority-low {
            background-color: #d4edda;
            color: #155724;
        }

        [data-theme="dark"] .priority-low {
            background-color: #1e3a25;
        }

        .task-actions {
            display: flex;
            gap: 8px;
        }

        .task-actions button {
            padding: 8px 12px;
            font-size: 14px;
        }

        .stats-container {
            display: flex;
            flex-wrap: wrap;
            gap: 15px;
            margin-bottom: 20px;
        }

        .stat-card {
            flex: 1;
            min-width: 150px;
            padding: 15px;
            background-color: white;
            border-radius: var(--border-radius);
            box-shadow: var(--box-shadow);
            text-align: center;
        }

        [data-theme="dark"] .stat-card {
            background-color: #3a3f44;
        }

        .stat-value {
            font-size: 24px;
            font-weight: 700;
            color: var(--primary-color);
            margin-bottom: 5px;
        }

        .stat-label {
            font-size: 14px;
            color: #666;
        }

        [data-theme="dark"] .stat-label {
            color: #aaa;
        }

        .history-container {
            margin-top: 30px;
        }

        .history-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 15px;
        }

        .history-item {
            padding: 10px;
            margin-bottom: 8px;
            background-color: #f8f9fa;
            border-radius: var(--border-radius);
            font-size: 14px;
            color: #666;
        }

        [data-theme="dark"] .history-item {
            background-color: #3a3f44;
            color: #aaa;
        }

        .history-time {
            color: #999;
            font-size: 12px;
            margin-right: 10px;
        }

        [data-theme="dark"] .history-time {
            color: #777;
        }

        .filter-controls {
            display: flex;
            flex-wrap: wrap;
            gap: 10px;
            margin-bottom: 20px;
        }

        .no-tasks {
            text-align: center;
            padding: 30px;
            color: #666;
            font-style: italic;
        }

        [data-theme="dark"] .no-tasks {
            color: #aaa;
        }

        .tabs {
            display: flex;
            margin-bottom: 20px;
            border-bottom: 1px solid #ddd;
        }

        [data-theme="dark"] .tabs {
            border-bottom-color: #444;
        }

        .tab {
            padding: 10px 20px;
            cursor: pointer;
            border-bottom: 3px solid transparent;
            transition: all 0.3s ease;
        }

        .tab:hover {
            background-color: #f1f1f1;
        }

        [data-theme="dark"] .tab:hover {
            background-color: #3a3f44;
        }

        .tab.active {
            border-bottom-color: var(--primary-color);
            font-weight: 600;
            color: var(--primary-color);
        }

        .tab-content {
            display: none;
        }

        .tab-content.active {
            display: block;
        }

        .modal {
            display: none;
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background-color: rgba(0, 0, 0, 0.5);
            z-index: 1000;
            justify-content: center;
            align-items: center;
        }

        .modal-content {
            background-color: white;
            padding: 25px;
            border-radius: var(--border-radius);
            width: 90%;
            max-width: 500px;
            box-shadow: 0 5px 15px rgba(0, 0, 0, 0.3);
        }

        [data-theme="dark"] .modal-content {
            background-color: #3a3f44;
        }

        .modal-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 20px;
            padding-bottom: 10px;
            border-bottom: 1px solid #eee;
        }

        [data-theme="dark"] .modal-header {
            border-bottom-color: #444;
        }

        .modal-title {
            font-size: 20px;
            color: var(--secondary-color);
            margin: 0;
        }

        .close-modal {
            background: none;
            border: none;
            font-size: 24px;
            cursor: pointer;
            color: #999;
        }

        .close-modal:hover {
            color: var(--danger-color);
        }

        .modal-footer {
            display: flex;
            justify-content: flex-end;
            gap: 10px;
            margin-top: 20px;
            padding-top: 15px;
            border-top: 1px solid #eee;
        }

        [data-theme="dark"] .modal-footer {
            border-top-color: #444;
        }

        .whatsapp-form {
            margin-top: 20px;
        }

        .preview-container {
            margin: 15px 0;
            padding: 15px;
            background-color: #f8f9fa;
            border-radius: var(--border-radius);
            border: 1px dashed #ccc;
        }

        [data-theme="dark"] .preview-container {
            background-color: #343a40;
            border-color: #555;
        }

        .preview-title {
            font-weight: 600;
            margin-bottom: 10px;
            color: var(--secondary-color);
        }

        .theme-toggle {
            position: fixed;
            top: 20px;
            right: 20px;
            background-color: var(--primary-color);
            color: white;
            border: none;
            border-radius: 50%;
            width: 40px;
            height: 40px;
            display: flex;
            align-items: center;
            justify-content: center;
            cursor: pointer;
            box-shadow: var(--box-shadow);
            z-index: 1000;
        }

        .theme-toggle:hover {
            background-color: var(--secondary-color);
        }

        .export-controls {
            display: flex;
            gap: 10px;
            margin-top: 20px;
        }

        @media (max-width: 768px) {
            .task-item {
                flex-direction: column;
                align-items: flex-start;
            }

            .task-content {
                margin-right: 0;
                margin-bottom: 10px;
            }

            .task-actions {
                width: 100%;
                justify-content: flex-end;
            }

            .modal-content {
                width: 95%;
                padding: 15px;
            }

            .export-controls {
                flex-direction: column;
            }
        }