This example displays a single static paragraph element reading “yay” on a blank page. It uses D3 v7 to select the page’s `#app` container and append a `<p>` tag with that text. The code imports the full D3 library as an ES6 module and relies on `d3.select` and `.append`, while the HTML includes a large sans-serif font style for the body. No data or complex visualization is shown.