This example visualizes a city connectivity network using a force-directed graph. Seven U.S. cities are rendered as labeled circles, with grey lines connecting them to show direct links. The layout is computed live with `d3.forceSimulation`, combining `forceLink`, `forceManyBody`, and `forceCenter` to position nodes. The graph is drawn as SVG elements, and users can drag any node to reposition it, with the simulation updating the links and labels in real time.