This example reproduces a Sol LeWitt-inspired geometric composition using D3 v7. It renders a grid of alternating horizontal and vertical SVG rectangles that are masked to reveal a circular viewing window at the center of the page. The code uses `d3.select` and `d3.range` to generate 100 rect elements per direction, with two distinct SVG masks (`circle-mask` and `circle-mask2`) that control visibility by combining black and white fill shapes. The visualization is entirely procedural, with no external data source, and adapts to the full browser viewport.