One scene function, two games, two renderers, running at the same time on this page. Sprites, a lit and shiny mesh, a floor, particles and a dither post chain, all drawn by both. The scene never learns which backend it is on.
The two are held to pixel parity by a comparison suite, not by eye. Where they still differ it is by a handful of pixels at a quantisation boundary or a shadow's penumbra. If your browser has no WebGPU the left panel says so: the fallback demonstrating itself.