Two copies of one grid, one mask, one point
Exploded isometric view of the cursor spotlight layers Three tilted planes stacked with gaps: a light dot grid, a radial mask disc, and a black dot grid clipped by that mask. A fourth plane below shows the composite. A dashed vertical guide runs from a cursor marker through the disc center on every plane. 1 light grid background: the dot tile always visible 2 the mask mask-image: radial-gradient( 100px at cursor, 100% · 80% @25% · 40% @55% · 0 @rim) 3 dark grid, masked same tile, black mask-image applied: only the disc paints cursor · clientX, clientY every disc is centered here flattened = what you see 1 + (3 through 2) dots darken, nothing moves