An SVG grid of 100 horizontal and 100 vertical rectangles covers the full viewport. Two circular masks, defined via D3's `mask` element, create a lens-like effect: the first mask exposes a central white circle outlined by black-filled rectangles, while the second inverts the fill to produce a complementary pattern. Using D3 v7's `join` method, the code binds `d3.range` data to generate the rectangles, with each strip sized 10 pixels thick and spaced 20 pixels apart. The overlapping masks reveal alternating stripe orientations, forming a dynamic moiré-like crosshatch within the central circular region.