A dynamic animation of circles shows a sinusoidal wave pattern, with each circle's vertical position and radius oscillating over time. The visualization builds on D3.js, using the `select` API to append an SVG canvas and the `.join()` method to efficiently update circle elements each frame. Data is generated procedurally in `makeData` with a sine-based formula, driven by a 60 FPS `setInterval` timer that increments a time variable. The visual result is a smooth, continuous motion of scaling and bobbing circles across the screen.