This example shows a simple four-node network graph with edges connecting nodes 1–4 in a small undirected graph. The visualization uses D3.js v7’s `d3.forceSimulation` with a `forceLink`, charge, and center force to position the nodes and update their coordinates on each tick. Nodes are rendered as SVG circles with class `node`, and edges as SVG lines with class `edge`. The data is hardcoded in the script, and no external dataset or interaction is present.