A force-directed particle system in SVG uses D3 v3’s `d3.layout.force` to simulate 200 circles with random radii, while a fixed center node applies a strong negative charge to repel others. A quadtree (`d3.geom.quadtree`) accelerates collision detection, and the layout’s `on("tick")` event updates circle positions. Mouse movement drives the root node’s velocity via `d3.mouse`, resuming the simulation. The visualization runs in React, though the rendering logic is pure D3.