This example renders a static SVG grid of thin vertical and horizontal lines across the full browser window, creating a Cartesian coordinate system. The code uses raw DOM manipulation with `document.createElementNS` to append individual `rect` elements to an SVG, along with helper functions `grid`, `printPattern`, and `printDiag` that position blue filled cells. It demonstrates generating geometric shapes, including diagonal lines, by placing 10-pixel squares at calculated grid intersections. No external libraries are used; the visualization relies solely on vanilla JavaScript to build the SVG structure.