Animated D3 selection exploration shows a variable number of circles moving in a sine-wave pattern across an SVG canvas. The visualization demonstrates D3's selection API, specifically the `join` operation for efficiently managing entering, updating, and exiting nodes as the data array changes over time. Using `setInterval` to update a time parameter every 200 milliseconds, the code generates new data points via `range` and applies `attr` updates for position and radius. The example forks a v3-era D3 exploration and renders with standard SVG animation.