This example demonstrates how D3 SVG masks can create overlapping geometric patterns. It generates 100 horizontal and 100 vertical rectangles, then applies two distinct masks with inverted fill rules to reveal or hide different regions. The code uses D3’s `select`, `range`, `symbols`, and `symbol` APIs to draw predefined symbol shapes within each mask. The visualization fills the browser window, with symbol paths placed at regular intervals across the width, producing a dynamic interplay between the grid lines and masked shapes.