This example shows a fullscreen grid of 200 vertical rectangles, each a random color, animating upward indefinitely. The rendering approach uses raw SVG elements created via the `document.createElementNS` API, with styles set directly on each rectangle. The animation relies on the Web Animations API (`element.animate`) to translate each rectangle along the Y-axis with randomized durations and infinite iterations. No external JavaScript libraries are used; the page is a minimal HTML document with inline CSS and JavaScript, demonstrating basic D3-free DOM manipulation for a generative visual effect.