Learning D3
This example demonstrates the simplest possible D3 setup: a blank HTML page that uses D3 version 6 to append an SVG element to the body and turn its background green. The visualization shows no data or chart—only a colored rectangle filling the viewport. The code relies on the `select` method from the `d3` module to target the body, then chains `.append("svg")` and `.style("background", "green")` to create and style the SVG. The page loads d3.v6 from a CDN and renders the result in a web browser.