This example demonstrates a generative animation of circles floating across the browser window. A sine wave controls both the number of circles and their vertical position, creating a smooth, undulating motion. Using D3 version 7, the code selects the empty SVG element and dynamically joins circle elements, updating their `cx`, `cy`, and `r` attributes each frame. The animation runs on a 60 FPS interval, directly manipulating SVG attributes in a minimal, function-based approach without any data source.