Back in 2013 the game magazine Polygon created really stunning illuminations in their Playstation 4 and Xbox One reviews. It's what got my interested in the more advanced uses of SVG and CSS -- it uses a clever trick where it uses the bezier curves as paths that are then filled in by offsetting the stroke fill... here it is.
stroke-dasharray: 422px, 422px;
stroke-dashoffset: 0px;
fill: rgba(255, 255, 255, 0.333);