A full-window SVG smiley face is drawn with a yellow circle, two black eyes, and a mouth created using D3's `arc` path generator. The React component computes the layout from `window.innerWidth` and `window.innerHeight`, centering the face and scaling the head radius based on viewport height. D3 v7's `arc()` is used to define the mouth with a specified inner radius, width, and angular range, while React 16.9 renders the SVG elements declaratively. The visualization adapts to the browser window size and uses a minimal, static composition.