body {
            font-family: sans-serif;
            background-color: #f9f9f9;
            margin: 0;
            padding: 20px;
            display: flex;
            flex-direction: column;
            align-items: center;
        }

        #controls {
            text-align: center;
            margin-bottom: 20px;
        }

        svg {
            background-color: white;
            border: 1px solid #ddd;
            border-radius: 8px;
            box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
        }

        .node {
            cursor: pointer;
        }

        .node circle {
            fill: #fff;
            stroke: #4682b4;
            stroke-width: 2px;
        }

        .node text {
            font: 12px sans-serif;
        }

        .link {
            fill: none;
            stroke: #ccc;
            stroke-width: 1.5px;
        }