This example demonstrates a dynamic collection of circles that undulate across the screen, with each circle’s position and radius varying sinusoidally over time. The animation runs at 60 frames per second using a `setInterval` callback. It leverages D3’s `select` and `range` modules to build and update the SVG scene, while a custom `vizData` function uses D3’s selection `.join()` API to create or update circles based on newly generated data. The data itself is produced by `makeData`, which computes x, y, and r values from time and index parameters.