A grid of thin horizontal and vertical rectangles covers the screen, but two circular masks reveal only the central region: one mask shows the horizontal lines, the other shows the vertical lines, creating a crosshatch pattern inside an overlapping circle. The example uses D3 v7’s `select`, `range`, and `join` to generate 100 SVG `<rect>` elements per direction, with `mask` elements and black/white filled circles controlling visibility. The full-screen SVG renders in the browser with no external data.