This example renders a full-screen SVG smiley face using React and D3. It computes the face dimensions from the browser window size and centers the drawing with a D3 arc for the mouth, alongside circles for the head, eyes, and stroke. The code uses ReactDOM to mount the component and d3.arc to generate the mouth path, with all shapes positioned relatively to a central transform group. The visualization is static, demonstrating basic geometric composition with D3 path generation inside a React component.