:root {
            --primary-color: #2c7da0;
            --secondary-color: #a9d6e5;
            --accent-color: #01497c;
            --light-gray: #f8f9fa;
            --border-color: #eaeaea;
            --text-color: #333;
            --text-muted: #6c757d;
            --success-color: #28a745;
            --warning-color: #ffc107;
            --math-color: #6f42c1;
            --calc-color: #e83e8c;
            --contour-color: #20c997;
        }
         .page-header {
            background: linear-gradient(135deg, rgba(169, 214, 229, 0.4) 0%, rgba(44, 125, 160, 0.4) 100%);
            padding: 1.5rem 0;
            margin-bottom: 2rem;
            border-bottom: 1px solid rgba(44, 125, 160, 0.2);
            position: relative;
            overflow: hidden;   color: var(--text-color);
        }
        .breadcrumb {
            background-color: transparent;
            padding: 0.5rem 0;
            margin-bottom: 0.5rem;
        }
        .breadcrumb-item a {
            color: var(--text-muted);
            text-decoration: none;
        }
        .breadcrumb-item.active {
            color: var(--text-color);
        }
        .form-control:focus {
            border-color: var(--primary-color);
            box-shadow: 0 0 0 3px rgba(44, 125, 160, 0.15);
        }
        .math-input {
            font-family: 'Cambria Math', 'Latin Modern Math', STIXGeneral, serif;
            font-size: 1.1rem;
        }
        .math-result {
            padding: 12px;
            background-color: white;
            border-radius: 4px;
            border: 1px solid #eee;
            font-size: 1.1rem;
            font-family: 'Cambria Math', 'Latin Modern Math', STIXGeneral, serif;
            margin: 10px 0;
            text-align: center;
        }
        .math-equation {
            font-size: 1.3rem;
            padding: 15px;
            background-color: rgba(111, 66, 193, 0.05);
            border-left: 4px solid var(--math-color);
            border-radius: 4px;
            margin: 15px 0;
        }
        .viz-container {
            position: relative;
            height: 500px;
            width: 100%;
            margin: 1.5rem 0;
            border: 1px solid var(--border-color);
            border-radius: 6px;
            overflow: hidden;
        }
        .viz-tabs {
            display: flex;
            border-bottom: 1px solid var(--border-color);
            background-color: var(--light-gray);
        }
        .viz-tab {
            padding: 0.75rem 1.5rem;
            cursor: pointer;
            border-right: 1px solid var(--border-color);
            font-weight: 500;
            transition: all 0.3s;
        }
        .viz-tab:hover {
            background-color: rgba(44, 125, 160, 0.1);
        }
        .viz-tab.active {
            background-color: white;
            color: var(--primary-color);
            border-bottom: 2px solid var(--primary-color);
        }
        .viz-content {
            height: calc(100% - 48px);
            position: relative;
        }
        .math-box {
            background-color: rgba(111, 66, 193, 0.05);
            border-left: 3px solid var(--math-color);
            padding: 1rem;
            border-radius: 0 4px 4px 0;
            margin: 1.5rem 0;
        }
        .contour-box {
            background-color: rgba(32, 201, 151, 0.05);
            border-left: 3px solid var(--contour-color);
            padding: 1rem;
            border-radius: 0 4px 4px 0;
            margin: 1.5rem 0;
        }
        @media (max-width: 768px) {
            .viz-container {
                height: 400px;
            }
        }
        .function-examples {
            display: flex;
            flex-wrap: wrap;
            gap: 0.5rem;
            margin: 1rem 0;
        }
        .example-btn {
            background-color: rgba(44, 125, 160, 0.1);
            border: 1px solid rgba(44, 125, 160, 0.2);
            border-radius: 4px;
            padding: 0.5rem 0.75rem;
            font-size: 0.9rem;
            color: var(--primary-color);
            cursor: pointer;
            transition: all 0.2s;
            font-family: 'Courier New', monospace;
        }
        .example-btn:hover {
            background-color: rgba(44, 125, 160, 0.2);
            transform: translateY(-2px);
        }
        .math-notation {
            font-family: 'Cambria Math', 'Latin Modern Math', STIXGeneral, serif;
            font-size: 1.1rem;
        }
        .calculation-step {
            margin-bottom: 1.5rem;
            padding-bottom: 1.5rem;
            border-bottom: 1px dashed var(--border-color);
        }
        .contour-levels {
            display: flex;
            flex-wrap: wrap;
            gap: 0.75rem;
            margin: 1rem 0;
        }
        .level-badge {
            background-color: rgba(32, 201, 151, 0.1);
            border: 1px solid rgba(32, 201, 151, 0.3);
            border-radius: 20px;
            padding: 0.25rem 0.75rem;
            font-size: 0.85rem;
            color: #0a7c5f;
        }
        .level-value {
            font-weight: 600;
        }
        .color-scale {
            height: 20px;
            width: 100%;
            border-radius: 4px;
            margin: 1rem 0;
            background: linear-gradient(to right, #440154, #3b528b, #21918c, #5ec962, #fde725);
        }
        .scale-labels {
            display: flex;
            justify-content: space-between;
            font-size: 0.8rem;
            color: var(--text-muted);
        }
        .graph-controls {
            display: flex;
            flex-wrap: wrap;
            gap: 1rem;
            margin: 1rem 0;
            padding: 1rem;
            background-color: var(--light-gray);
            border-radius: 6px;
        }
        .control-group {
            display: flex;
            align-items: center;
            gap: 0.5rem;
        }
        .control-label {
            font-weight: 500;
            font-size: 0.9rem;
        }
        .surface-props {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
            gap: 1rem;
            margin: 1.5rem 0;
        }
        .prop-card {
            background: white;
            border-radius: 6px;
            padding: 1rem;
            border: 1px solid var(--border-color);
            text-align: center;
        }
        .prop-value {
            font-size: 1.25rem;
            font-weight: 700;
            color: var(--primary-color);
            margin-bottom: 0.25rem;
        }
        .prop-label {
            color: var(--text-muted);
            font-size: 0.85rem;
        }
        .progress-container {
            display: none;
            margin: 1rem 0;
        }
        .progress-bar {
            height: 10px;
            border-radius: 5px;
            background-color: #e9ecef;
            overflow: hidden;
        }
        .progress-fill {
            height: 100%;
            background-color: var(--primary-color);
            width: 0%;
            transition: width 0.3s ease;
        }
        .progress-text {
            display: flex;
            justify-content: space-between;
            font-size: 0.85rem;
            margin-top: 0.25rem;
            color: var(--text-muted);
        }
        .modal-overlay {
            display: none;
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background-color: rgba(0, 0, 0, 0.5);
            z-index: 1100;
            align-items: center;
            justify-content: center;
        }
        .modal-content {
            background-color: white;
            border-radius: 8px;
            padding: 2rem;
            max-width: 500px;
            width: 90%;
            box-shadow: 0 4px 20px rgba(0, 0, 0, 0.15);
        }
        .modal-title {
            font-weight: 600;
            margin-bottom: 1rem;
            color: var(--primary-color);
        }
        .settings-container {
            display: flex;
            gap: 0.5rem;
            margin-top: 0.5rem;
        }
        .settings-btn {
            font-size: 0.85rem;
            padding: 0.4rem 0.75rem;
        }
        .point-info-panel {
            position: absolute;
            top: 10px;
            right: 10px;
            background-color: rgba(255, 255, 255, 0.95);
            border: 1px solid var(--border-color);
            border-radius: 6px;
            padding: 1rem;
            width: 250px;
            z-index: 100;
            box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
            display: none;
        }
        .point-info-title {
            font-weight: 600;
            margin-bottom: 0.5rem;
            color: var(--primary-color);
        }
        .point-info-content {
            font-size: 0.9rem;
        }
        .point-coordinate {
            font-family: 'Courier New', monospace;
            background-color: rgba(44, 125, 160, 0.1);
            padding: 0.25rem 0.5rem;
            border-radius: 4px;
            margin: 0.25rem 0;
        }
        .presets-container {
            display: flex;
            flex-wrap: wrap;
            gap: 0.75rem;
            margin: 1rem 0;
        }
        .preset-btn {
            background-color: white;
            border: 1px solid var(--border-color);
            border-radius: 6px;
            padding: 0.75rem;
            width: 120px;
            cursor: pointer;
            transition: all 0.2s;
            text-align: center;
        }
        .preset-btn:hover {
            background-color: var(--light-gray);
            border-color: var(--primary-color);
        }
        .preset-name {
            font-weight: 600;
            font-size: 0.9rem;
            margin-bottom: 0.25rem;
            color: var(--primary-color);
        }
        .preset-formula {
            font-family: 'Courier New', monospace;
            font-size: 0.8rem;
            color: var(--text-muted);
        }