Intro D3.js
This example shows a simple SVG canvas that turns red as a minimal introduction to D3.js. The page loads D3 v5 from a CDN and uses the `d3.select` method to target the `<svg>` element, then applies a red background color directly to it. The visualization is rendered with SVG, and the styling is complemented by an external stylesheet that imports the Ubuntu font. No data is involved; the example focuses solely on demonstrating basic DOM selection and manipulation with D3.