This example shows a force-directed network of city flight routes, with nodes representing cities and links representing connections. Major hubs like New York and Tokyo are drawn as larger, blue circles, while non-hub cities appear as smaller, orange circles. The visualization uses D3.js v7 with `d3.forceSimulation`, `d3.forceLink`, `d3.forceManyBody`, `d3.forceCenter`, and `d3.drag` to position the nodes dynamically. The SVG output renders nodes and edges, with labels showing city names.