This example builds a simple cartoon face using SVG circles. It constructs a yellow head, two black eyes, and no other facial features. The code creates the face by directly appending `circle` elements to the `svg` with specific `cx`, `cy`, and `r` attributes. It uses the D3 v5 selection and mutation API, specifically `select('svg')` and `svg.append('circle')`, to position the elements based on the SVG's `width` and `height` attributes. The face is rendered using SVG, with styling applied via CSS.