Horizontal and vertical stripes cross an SVG canvas to form a grid, while two mask layers reveal or hide rows and columns based on overlapping d3 symbols. The code uses d3.select, range, join, and symbol to generate 100 rectangles in each direction, with masks built via d3.mask and inverted fills. Both masks position five symbol paths (from d3.symbols) across the center, controlling visibility of the striped pattern. The rendering relies entirely on SVG elements and D3’s data-join to create the layered visual effect.