This example demonstrates how to draw a face using D3.js. The visualization fills the browser viewport with a rounded rectangle, created by chaining `select` and `attr` methods on the SVG element. It uses the `d3.select` API to target the SVG container and appends a styled rectangle shape. The code calculates the drawing area dimensions from the document body’s client width and height. This serves as a minimal, geometric illustration of D3’s SVG rendering capabilities without any external data.