Zapline — Référence de design web et prompt

# Prompt: Zapline trading CTA hero ("Royal Violet")

Build a single-file, one-screen **trading-product hero** for a fictional on-chain trading tool, **Zapline**. Use plain HTML, CSS and vanilla JS, with no framework and no build step. The look is a pure black starfield with the glowing violet rim of a giant planet arching across the top. A big bold headline sits under it, and a dark product dashboard rises from the bottom of the screen with a violet light line along its top edge.

## Media

- **Glow video:** `https://d2ol7oe51mr4n9.cloudfront.net/user_38xzZboKViGWJOttwIXH07lWA1P/e859f229-8ebd-43fb-a5a0-58006ba75327.mp4` (1460×624, 4s, muted, loops).
  - **Content:** the violet and magenta planet rim on black. The glow pulses, plasma ripples along the arc, light streaks race outward, and the camera pushes in slowly.
  - **Loop:** the last second crossfades into the first, so it loops without a jump and never plays in reverse.
  - **Placement:** desktop only. Lay it over the star layer with `mix-blend-mode: screen` so its black stays transparent. It covers the top 1672×717 design px of the stage, and fades in (0.8s) when ready.
- **Fallback:** until then (and on phones), the rim is painted on a canvas from a small polar colour table, `panel-texture.png` / `chart-texture.png` (violet, embedded).
- **Stars:** procedural white dots on a canvas.