The other Labs pages have a sparse twinkling background visible right now behind this text. It's a single SVG with a handful of <circle> elements, each driven by an independent CSS keyframe animation. All the per-frame work happens in the browser's compositor, so CPU cost is effectively zero.
The sliders below drive those parameters. Whatever you set here is saved to localStorage and applied to every other Labs page on this device. The background re-renders live as you drag; the page you're on is the same canvas, so you can preview against real content.
The background switch above is the master: the ambient field ships off and only animates on devices where it's been turned on here. The setting persists in localStorage and applies to every Labs page on this device; reset restores the defaults, which includes turning it back off.
One detail worth noting: the dot positions come from a saved seed, not a fresh roll, so the same field reappears on every refresh and on every other Labs page; you keep whatever layout you've got. The sliders here control density and timing against that fixed layout; dragging them previews the change without moving the dots (raising count appends new dots rather than reshuffling). The regenerate positions button rolls a new seed when you want a different field; reset restores the default settings but leaves the layout alone.
This ambient field is the calm cousin of two other Conway experiments on the site: Conway in ambient mode, the live Game of Life running under the page that this settings panel grew out of, and Conway on the GPU, the same simulation packed into a texture and stepped in a shader.