This example demonstrates D3 selections and data joins through an animated swarm of circles whose count, position, and size shift continuously over time. It uses `d3.select`, `d3.range`, and `data().join()` to bind an array of simulated points to SVG circle elements, updating their `cx`, `cy`, and `r` attributes in a 60fps `setInterval` loop. The animation responds to a sine-based time variable, creating smooth, organic motion. Rendering happens entirely in SVG within a full-window viewport.