A force-directed graph starter example renders three nodes and two links as SVG circles and lines. The simulation uses `d3.forceSimulation` with `forceManyBody` for repulsion, `forceLink` for connections, and `forceCenter` to keep the layout centered. On each tick, node and link positions update directly via the `simulation.on('tick')` handler, assigning `cx`, `cy`, and line endpoints from the simulation's coordinates. The data is hardcoded as three objects and two link pairs in D3 v7.