:root {
            --primary-color: #2c7da0;
            --secondary-color: #a9d6e5;
            --accent-color: #01497c;
            --construction-color: #d9534f;
            --concrete-color: #6c757d;
            --light-gray: #f8f9fa;
            --border-color: #eaeaea;
            --text-color: #333;
            --text-muted: #6c757d;
            --success-color: #28a745;
            --warning-color: #ffc107;
        }
        .skip-nav {
            position: absolute;
            top: -40px;
            left: 0;
            background: var(--primary-color);
            color: white;
            padding: 8px;
            z-index: 100;
            text-decoration: none;
        }
        .skip-nav:focus {
            top: 0;
        }
      .page-header {
            background: linear-gradient(135deg, rgba(169, 214, 229, 0.4) 0%, rgba(217, 83, 79, 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);
        }
        .shape-options {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(100px, 1fr));
            gap: 1rem;
            margin-bottom: 1.5rem;
        }
        .shape-option {
            border: 2px solid var(--border-color);
            border-radius: 8px; 
            text-align: center;
            cursor: pointer;
            transition: all 0.3s;
            background-color: white;
        }
        .shape-option:hover {
            border-color: var(--secondary-color);
            transform: translateY(-3px);
            box-shadow: 0 5px 15px rgba(0,0,0,0.05);
        }
        .shape-option.selected {
            border-color: var(--construction-color);
            background-color: rgba(217, 83, 79, 0.05);
        }
        .shape-icon {
            font-size: 2.5rem;
            color: var(--concrete-color);
            margin-bottom: 0.5rem;
        }
        .shape-name {
            font-weight: 600;
            color: var(--text-color);
        }
        .dimension-inputs {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
            gap: 1rem;
            margin-bottom: 1.5rem;
        }
        .dimension-group {
            display: flex;
            flex-direction: column;
        }
        .dimension-label {
            display: flex;
            align-items: center;
            margin-bottom: 0.5rem;
        }
        .dimension-label i {
            margin-right: 0.5rem;
            color: var(--construction-color);
        }
        .density-options {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
            gap: 1rem;
            margin-bottom: 1.5rem;
        }
        .density-option {
            border: 2px solid var(--border-color);
            border-radius: 8px;
            padding: 1rem;
            cursor: pointer;
            transition: all 0.3s;
            background-color: white;
        }
        .density-option:hover {
            border-color: var(--secondary-color);
        }
        .density-option.selected {
            border-color: var(--construction-color);
            background-color: rgba(217, 83, 79, 0.05);
        }
        .density-name {
            font-weight: 600;
            color: var(--text-color);
            margin-bottom: 0.25rem;
        }
        .density-value {
            color: var(--text-muted);
            font-size: 0.9rem;
        }
        .calculation-results {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
            gap: 1.5rem;
            margin-bottom: 1.5rem;
        }
        .result-card {
            background: white;
            border-radius: 8px;
            padding: 1.5rem;
            text-align: center;
            border: 1px solid var(--border-color);
            box-shadow: 0 2px 5px rgba(0,0,0,0.05);
        }
        .result-value {
            font-size: 2rem;
            font-weight: 700;
            color: var(--construction-color);
            margin-bottom: 0.5rem;
        }
        .result-label {
            color: var(--text-muted);
            font-size: 0.9rem;
        }
        .calculation-steps {
            margin-top: 1.5rem;
        }
        .calculation-step {
            margin-bottom: 1.5rem;
            padding-bottom: 1.5rem;
            border-bottom: 1px dashed var(--border-color);
        }
        .step-formula {
            background-color: rgba(44, 125, 160, 0.05);
            padding: 1rem;
            border-radius: 4px;
            border-left: 4px solid var(--primary-color);
            margin: 0.5rem 0;
            font-family: 'Courier New', monospace;
        }
        .unit-converter {
            background-color: white;
            border-radius: 8px;
            padding: 1.5rem;
            border: 1px solid var(--border-color);
            margin-top: 1.5rem;
        }
        .unit-grid {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
            gap: 1rem;
            margin-top: 1rem;
        }
        .concrete-box {
            background-color: rgba(217, 83, 79, 0.05);
            border-left: 3px solid var(--construction-color);
            padding: 1rem;
            border-radius: 0 4px 4px 0;
            margin: 1.5rem 0;
        }
        .density-table {
            width: 100%;
            border-collapse: collapse;
            margin: 1.5rem 0;
        }
        .density-table th, .density-table td {
            padding: 0.75rem;
            text-align: left;
            border: 1px solid var(--border-color);
        }
        .density-table th {
            background-color: var(--light-gray);
            font-weight: 600;
        }
        .density-table tr:nth-child(even) {
            background-color: rgba(44, 125, 160, 0.05);
        }
        @media (max-width: 768px) {
            .shape-options {
                grid-template-columns: repeat(2, 1fr);
            }
            .dimension-inputs {
                grid-template-columns: 1fr;
            }
            .calculation-results, .unit-grid {
                grid-template-columns: 1fr;
            }
        }
        .shape-visualization {
            display: flex;
            justify-content: center;
            align-items: center;
            margin: 1.5rem 0;
            padding: 1.5rem;
            background-color: var(--light-gray);
            border-radius: 8px;
            min-height: 200px;
        }
        .shape-diagram {
            width: 200px;
            height: 150px;
            position: relative;
        }
        .slab-diagram {
            width: 180px;
            height: 120px;
            background-color: var(--concrete-color);
            position: relative;
            border-radius: 4px;
        }
        .slab-length {
            position: absolute;
            bottom: -25px;
            width: 100%;
            text-align: center;
            font-size: 0.8rem;
        }
        .slab-width {
            position: absolute;
            right: -40px;
            top: 50%;
            transform: translateY(-50%);
            font-size: 0.8rem;
        }
        .slab-thickness {
            position: absolute;
            left: -40px;
            top: 50%;
            transform: translateY(-50%);
            font-size: 0.8rem;
        }
        .cylinder-diagram {
            width: 120px;
            height: 180px;
            background-color: var(--concrete-color);
            border-radius: 60px/90px;
            position: relative;
        }
        .cylinder-diameter {
            position: absolute;
            bottom: -25px;
            width: 100%;
            text-align: center;
            font-size: 0.8rem;
        }
        .cylinder-height {
            position: absolute;
            right: -40px;
            top: 50%;
            transform: translateY(-50%);
            font-size: 0.8rem;
        }
        .column-diagram {
            width: 100px;
            height: 180px;
            background-color: var(--concrete-color);
            position: relative;
        }
        .column-length {
            position: absolute;
            bottom: -25px;
            width: 100%;
            text-align: center;
            font-size: 0.8rem;
        }
        .column-width {
            position: absolute;
            right: -40px;
            top: 50%;
            transform: translateY(-50%);
            font-size: 0.8rem;
        }
        .column-height {
            position: absolute;
            left: -40px;
            top: 50%;
            transform: translateY(-50%);
            font-size: 0.8rem;
        }
        .wall-diagram {
            width: 180px;
            height: 100px;
            background-color: var(--concrete-color);
            position: relative;
            border-radius: 4px;
        }
        .wall-length {
            position: absolute;
            bottom: -25px;
            width: 100%;
            text-align: center;
            font-size: 0.8rem;
        }
        .wall-height {
            position: absolute;
            right: -40px;
            top: 50%;
            transform: translateY(-50%);
            font-size: 0.8rem;
        }
        .wall-thickness {
            position: absolute;
            left: -40px;
            top: 50%;
            transform: translateY(-50%);
            font-size: 0.8rem;
        }
        .unit-toggle {
            display: flex;
            align-items: center;
            justify-content: center;
            margin-bottom: 1.5rem;
        }
        .toggle-label {
            margin: 0 1rem;
            font-weight: 600;
        }
        .toggle-switch {
            position: relative;
            display: inline-block;
            width: 60px;
            height: 30px;
        }
        .toggle-switch input {
            opacity: 0;
            width: 0;
            height: 0;
        }
        .toggle-slider {
            position: absolute;
            cursor: pointer;
            top: 0;
            left: 0;
            right: 0;
            bottom: 0;
            background-color: #ccc;
            transition: .4s;
            border-radius: 30px;
        }
        .toggle-slider:before {
            position: absolute;
            content: "";
            height: 22px;
            width: 22px;
            left: 4px;
            bottom: 4px;
            background-color: white;
            transition: .4s;
            border-radius: 50%;
        }
        input:checked + .toggle-slider {
            background-color: var(--construction-color);
        }
        input:checked + .toggle-slider:before {
            transform: translateX(30px);
        }
        .form-text {
            font-size: 0.875rem;
            color: var(--text-muted);
            margin-top: 0.25rem;
        }
        .social-icons {
            display: flex;
            gap: 1rem;
            margin-top: 1rem;
        }
        .social-icon {
            width: 36px;
            height: 36px;
            border-radius: 50%;
            background-color: var(--light-gray);
            display: flex;
            align-items: center;
            justify-content: center;
            color: var(--text-muted);
            text-decoration: none;
            transition: all 0.3s;
        }
        .social-icon:hover {
            background-color: var(--primary-color);
            color: white;
        }
        .faq-section {
            margin-top: 2rem;
        }
        .accordion-button:not(.collapsed) {
            background-color: rgba(44, 125, 160, 0.1);
            color: var(--primary-color);
        }
        .accordion-button:focus {
            box-shadow: 0 0 0 0.25rem rgba(44, 125, 160, 0.25);
        }
        :focus {
            outline: 2px solid var(--primary-color);
            outline-offset: 2px;
        }
        @media print {
            .navbar, .page-header, .action-, .ad-container, .related-tools, .footer, .btn {
                display: none !important;
            }
            }