This example shows a force-directed network of 13 nodes connected by 17 links, with nodes colored by group using a categorical scale and link thickness varying with edge weight. The visualization loads node and link data from a JSON file and renders it as SVG circles and lines. It uses `d3.forceSimulation` with `d3.forceLink`, `d3.forceManyBody`, and `d3.forceCenter` to compute the layout, updating node positions and link endpoints on each tick.