This example demonstrates a simple SVG visualization that dynamically resizes to fill the browser window. It uses CSS to define a full-viewport container and JavaScript to read the container’s client dimensions on every window resize event. The code appends an SVG and redraws two crossing lines to form an X, updating the SVG’s width and height attributes. It relies on D3 v5’s selection and data-join methods (`selectAll`, `enter`, `merge`) to manage the line elements, with no external data source.