A full-window smiley face rendered with React 16.9 and SVG. The face is centered using the window dimensions and built from three circles: a yellow head with a black stroke, and two eye circles, all positioned with fixed offsets and radii. The code uses ReactDOM to mount the SVG component, with dimensions and coordinates derived from `window.innerWidth` and `window.innerHeight`. The mouth is not drawn, leaving the face incomplete.