This example renders a full-screen smiley face using React’s declarative SVG elements. It computes the face’s geometry—head radius, eye positions, and stroke width—from the browser window’s dimensions, centering the graphic dynamically. The code uses React 16.9 and ReactDOM to mount an SVG `<circle>` for the yellow head and two black eyes, with a mouth intentionally omitted from the current implementation. The layout adapts responsively to any viewport size through inline width and height calculations.