This example shows a full-screen pattern of intersecting horizontal and vertical bars, each rendered as a set of thin SVG rectangles. The bars are generated using `d3.range` and joined to `rect` elements, but only the central circular area is visible due to two SVG masks. The first mask reveals the horizontal bars through a white circle on a black background, while the second mask hides the vertical bars in the same region using a black circle on white. The result is a cross-hatched grid with a circular cutout, built with React and D3 v7.