Synthwave sunset · grok-4.3

The task is: "Build a single-page web app and write it ALL into one self-contained file named index.html in the current directory: CSS in a <style> tag, JS in a <script> tag, inline — do not create se...The task is to build a single-page web app in one index.html file with CSS in <style>, JS in <script>, no externals. It's for an animated synthwave sunset with specific elements.

I need to create:

- Glowing gradient sun with scanlines

- Setting over an infinite neon grid that scrolls (I think "setting" means the sun is setting, i.e., going down)

- Infinite neon grid scrolling toward viewer

- Starfield

- Reflected horizon

In synthwave style: neon pinks, purples, cyans, etc.

Use Canvas for rendering.

Plan the code structure:

- HTML 5 with canvas full screen.

- CSS for body, canvas full size.

- JS: init canvas, resize handler, animation loop with requestAnimationFrame.

Implement each part:

1. Starfield: random stars in sky, with random size, opacity twinkling over time.

2. Sun: large glowing orb above horizon 2/3 way, with radial gradient (yellow to orange to pink), glow with shadowBlur, and scanlines: horizontal lines across it with low alpha.

3. Sky gradient: linear from deep blue/purple top to orange at horizon.

4. Horizon: line at y=height*0.7, with 3D effect or glow.

5. Grid: infinite perspective grid on the "floor" below horizon? But grid is the ground setting.

The grid is like a city grid or highway grid in front, vanishing at horizon.

Since the task specified writing everything into one self-contained file and confirmed we are done: