This example shows a full-screen yellow smiley face rendered as a responsive SVG, with black stroke outlines, two eyes, and a mouth. It uses React 16.9 and ReactDOM to declaratively build the SVG elements, with dimensions calculated from `window.innerWidth` and `window.innerHeight`. The face is centered using a `transform` translation, and all shapes are positioned relative to that origin via props like `cx`, `cy`, `r`, and `stroke-width`.