.hub-guide {
            max-width: 1200px;
            margin: 0 auto;
            font-family: 'Helvetica Neue', Arial, sans-serif;
            line-height: 1.7;
            color: #2d3436;
            padding: 3rem 2rem;
            background: #fdfdfd;
        }

        .hub-chapter {
            margin: 4rem 0;
            position: relative;
        }

        .hub-title {
            font-size: 2.4rem;
            color: #2c3e50;
            padding-bottom: 1.2rem;
            border-bottom: 3px solid #3498db;
            margin-bottom: 3rem;
            letter-spacing: -0.5px;
        }

        .spec-box {
            background: #f8f9fa;
            border-left: 4px solid #2980b9;
            padding: 1.8rem;
            margin: 2rem 0;
            border-radius: 0 6px 6px 0;
            box-shadow: 0 3px 6px rgba(0,0,0,0.03);
        }

        .mechanical-table {
            width: 100%;
            border: 1px solid #dfe6e9;
            margin: 2.5rem 0;
            border-collapse: separate;
            border-spacing: 0;
            background: white;
        }

        .mechanical-table th {
            background: #3498db;
            color: white;
            padding: 1.2rem;
            font-weight: 600;
            border-right: 1px solid #2980b9;
        }

        .mechanical-table td {
            padding: 1.2rem;
            border-bottom: 1px solid #dfe6e9;
            border-right: 1px solid #dfe6e9;
        }

        .engineering-term {
            color: #c0392b;
            font-weight: 500;
            position: relative;
            padding-bottom: 2px;
            border-bottom: 2px dotted #e74c3c;
        }

        .hub-illustration {
            width: 100%;
            max-width: 800px;
            margin: 2rem auto;
            padding: 1.5rem;
            background: #ecf0f1;
            border-radius: 8px;
        }

        @media (max-width: 768px) {
            .hub-title {
                font-size: 1.8rem;
            }
            .hub-guide {
                padding: 2rem 1rem;
            }
        }