A reaction-diffusion coral pattern

Create a reaction-diffusion coral pattern: a generative artwork that people would leave running on a second screen.

What makes it great:
- A strong visual idea with a deliberate palette and composition, not random noise: a piece someone would choose to exhibit.
- Rich motion that keeps evolving: it never repeats exactly, never settles into a still image, and never turns to mush or blows out to white. Over a minute it passes through visibly different states.
- Depth and texture: layering, trails, gradients, light, and subtle variation in scale and speed.
- Driven by a system (noise fields, particles, recursion, simulation, shaders…) and seeded randomly, so each visit is different.

How it is shown:
- No text, buttons, controls or UI of any kind, and nothing to click: it plays on its own.
- It fills the whole window edge to edge at any size and shape, and composes well on a portrait phone too.
- It is striking from the very first frame: no fade-in from black and no empty canvas slowly filling up.

Make it astonishing. Both builds are shown side by side in a 30-second video on social media, where people decide in one second whether to stop scrolling:
- The very first frame is already striking: bold colour, light and motion, never an empty, plain or loading screen.
- Build to a signature moment within the first 10 seconds that makes people say "wow": a reveal, a transformation, an explosion of particles, a chain reaction.
- Go beyond the obvious version of the idea: choose a surprising, inventive take with its own world, mood and personality, not a generic template.
- Layer it: depth, glow and light, particles and trails, smooth easing, and detail that rewards both a glance and a closer look.
- It is watched at about half size on a phone: keep the important shapes big and high in contrast, and any key text large (at least 28 CSS pixels).
- Let something happen: within 30 seconds it passes through clearly different phases (for example calm, bloom, transformation, renewal), with at least one breathtaking moment.

Fixed rules (so every model is compared on the same terms):
- Exactly one file, index.html, in the current directory. Create no other files.
- Plain HTML, CSS and JavaScript. You may use three.js 0.170.0 from https://cdn.jsdelivr.net/npm/three@0.170.0/ (via an import map) if it helps. No other libraries, images, 3D models, fonts or network requests: build everything yourself in code (canvas, SVG, CSS or WebGL).
- It fills the browser window and works on a phone and on a desktop, with no page scrollbars.
- Animate with requestAnimationFrame and its timestamp so speed does not depend on the frame rate.

It must work in an ordinary browser on any graphics card. You cannot open a browser to look at it, so build it carefully:
- Every frame is fully drawn: no black, blank or flickering frames or patches. Keep any shader maths free of NaN and infinity (no division by a value that can reach zero, no pow() of a negative number, no normalize() of a zero-length vector), and clamp colours to a safe range before bloom or other post-processing.
- No errors in the browser console: if you use three.js, map "three" and "three/addons/" in the import map, and import everything you use.
- It runs smoothly on an ordinary laptop or phone: keep the pixel ratio at 2 or below, and avoid creating new objects every frame.
- It adapts when the window is resized or the phone is rotated.
- Do not hide errors: never wrap the main loop or whole functions in a try/catch that silently swallows them; fix the cause instead (a try/catch around storage or audio is fine).
- It stays stable for hours: no arrays that keep growing, no slow drift to black or white, and no loss of precision as time grows (wrap or rescale time inside shaders).

Before you finish, read your file once from top to bottom and make sure that:
- It starts moving on the first frame, and looks clearly different after 30 seconds.
- There is no text or control anywhere on the page.
- It fills a 390×844 phone window and a 1280×720 desktop window edge to edge.
- Nothing can throw an error in the browser console.

The battle video records about 30 seconds right after the page opens.

Everything else is your choice: the idea, the technique, palette and motion. Make it as striking and mesmerizing as you can. Do not ask questions; make reasonable choices.