Reaction–Diffusion

Gray–Scott, run until the pattern stops moving.

patterns.reaction · v1 · renderer canvas

Coral growth · F=0.055 k=0.062 · 192² grid · 3200 steps

[data-canvas-stage] { display: none; }

Drawn in the browser

This generator does not send you an image. The server sends a short description of one — the parameters below, plus a 32-byte key — and the drawing is done here, from the same byte stream the server would have used. That needs JavaScript, so with it switched off there is nothing to show.

The description itself is still public: /api/v1/g/patterns.reaction returns it, and the maths is in resources/js.

Coral growth · F=0.055 k=0.062 · 192² grid · 3200 steps

Controls · from schema()

Width

200 2048

Height

200 2048

Pattern

Feed rate F

0.005 0.09

Only used when the preset is Custom. Most of this range is a field that dies within a few hundred steps — that is the honest shape of the parameter space.

Kill rate k

0.03 0.075

Only used when the preset is Custom.

Grid

96 288

The simulation runs on a square grid and is sampled up to the canvas, so this is detail, not size.

Steps

200 12000

How long the reaction runs. Capped against the grid size so a slider drag cannot lock the tab.

Diffusion of u

0.2 1.2

Diffusion of v

0.1 0.7

Seed patches

1 60

The initial disturbance. Everything on screen grows out of these.

Colour

Palette size

2 12

Banding

Invert

Entropy source

Picking a source changes the story on the receipt, never the quality: anything below class A is mixed with the OS CSPRNG before it reaches you. This result actually came from RANDOM.ORG.

seed token JNFWHYQSETBGV5XMTJCJCC1QBC

Re-render keeps this token. Generate replaces it. That is the whole idea.

Burned into the corner before the file is written, so the image keeps its provenance wherever it ends up:

entropy in

16 bytes

stream used

298 bytes

rejections

duration

214 µs

palette

feed

0.06

kill

0.06

steps requested

3,200

steps run

3,200

cell updates

117,964,800

Seed receipt

Class A · Cryptographic

Atmospheric radio noise, sampled in Dublin moments ago.

source: RANDOM.ORG
observed: 2026-10-28T22:12:33+00:00
latency: 226ms
mixed with: csprng — always

https://www.random.org/randomness/ ↗

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The token is the seed, so this link recomputes the result rather than looking it up. No database, and it works for as long as v1 does.

This page and /api/v1/g/patterns.reaction run the same code. There is no private endpoint.

Reaction–Diffusion

Result

Measurements

Seed receipt

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