This example shows a network graph of seven countries connected by weighted links, with node labels and draggable circles colored by group. It uses the D3 v4 force layout via `d3.layout.force` to compute positions, with gravity, charge, and distance parameters, and renders nodes as SVG groups and links as SVG lines. Edge thickness reflects the `weight` property from the `graphFile.json` data, and the force simulation updates node transforms and link coordinates on each tick.