Two intersecting sets of thin horizontal and vertical lines form a grid across the full screen. D3 symbols (shapes) are used as masks to selectively reveal or hide sections of these lines, creating a pattern inspired by Sol LeWitt's wall drawings. The code uses `d3.select`, `d3.range`, `d3.symbol`, and `d3.symbols` to generate SVG rectangles and masked paths, with two mask layers applied in opposite color inversions.