This example demonstrates a minimal, full-screen grid of horizontal and vertical stripes that become visible only through two circular windows. Built with D3.js version 7, it uses the `select` API to append SVG elements, `range` to generate 100 coordinates, and iterative `join` operations to create and position the rects. Two SVG masks—one with a central white circle on a black field, the other inverted—define the circular reveal for the horizontal and vertical stripe layers, respectively.