KAIRN — Référence de design web et prompt

# Prompt: KAIRN Alpine 26 hero

Build a single-file, one-screen **landing hero for a premium ski-goggle brand**, **KAIRN** (collection "Alpine 26"). Use plain HTML, CSS and vanilla JS, with no framework and no build step. The look is light-mode winter editorial: a full-bleed photo of a model in an all-white puffer suit and white knit beanie, seated in the snow and looking up, wearing mirrored **ice-blue goggles** that reflect glacier peaks. The background is a calm, almost studio-clean pale icy sky with only a faint low mountain ridge and light snow.

## Scene

- **Plate:** the background is ONE 16:10 photo (1728×1080): `https://d2ol7oe51mr4n9.cloudfront.net/user_38xzZboKViGWJOttwIXH07lWA1P/18a4a3c1-2af7-4c4a-9045-f6ddff26f4ca.jpg`. `object-fit:cover`, position 50% 30% (phones: 50% 18%, then 50% 0).
- **Motion:** a 5s muted looping video of the same plate plays over it with **identical cover rules**: `https://d2ol7oe51mr4n9.cloudfront.net/user_38xzZboKViGWJOttwIXH07lWA1P/823d013d-bf03-4967-b08f-63c3752df435.mp4` (1152×720). Snow drifts across the frame, the model turns her head slightly and the goggle reflections glint.
  - Fade it in once its first frame is ready.
- **Readability:** a soft, cool navy side-shade (`rgba(22,52,84,.34)` → 0 by 55% from the left, and .2 at the far right) keeps white type readable on the pale sky.
- **Rule:** nothing in the scene is drawn or animated in code.