This example renders a simple smiley face composed of three SVG circles: a large yellow circle with a black stroke for the face and two smaller black circles for the eyes. The React component `App` returns the SVG markup directly, using JavaScript expressions within JSX curly braces to compute circle positions and dimensions relative to the viewport. The visualization demonstrates how React manages SVG rendering in the browser, with D3 loaded as a standalone library but not actively used in this static composition.