Reaction-Diffusion
two chemicals feeding on each other, forever

What you see on every new tab

Reaction-Diffusion fills the New Tab page with the Gray-Scott reaction: two imaginary chemicals that spread and feed on each other, growing the worm-like labyrinths, dividing spots and branching coral that turn up on animal skins and shells. It is coloured like lava, from near-black violet through purple and hot pink to orange, with pale yellow on the highest ridges.

Left alone, a Gray-Scott pattern grows into a fixed maze and stops. This one is kept changing by a sweeping front, a slow current and a steady rain of new seeds.

• Six stages: the chemistry moves through labyrinth, dividing spots, a lattice of spots, labyrinth again, pulsing spots and thick coral, then starts over, about every three minutes.
• A sweeping front: every 28 seconds a soft band crosses the whole screen in a random direction, and as it passes the pattern reorganises into the next stage.
• A slow current: the field drifts on a swirling flow that slides and bends the shapes without piling them up.
• Seeds: a new seed lands at a random spot every two seconds and grows into the current pattern.
• Opens grown: each new tab runs 1,500 steps before the first frame from a fresh random scatter of seeds, so it opens on a full pattern rather than dots.

The two chemicals are stored in a texture at half the screen's width, and a shader advances the Gray-Scott equations eight steps every frame. Another pass moves the field along the current, and a third shades it with an embossed light.

What it reacts to

• Mouse: moving the cursor wipes the chemicals clean in a small circle under it, leaving a dark trail that the pattern grows back into from the edges.
• Music: with music sync on, bass pulls the chemistry toward the dividing-spots stage, speeds the current and brightens the picture; a kick drops a fresh seed; treble brightens the ridges orange.
• Night: after sunset the shared night veil dims the whole page, reaching 60 percent at full night.

Free or Pro?Pro

Ambient New Tab is free to install, with five free themes. Reaction-Diffusion is a Pro theme. Pro is $5.99 a month or $39.99 a year, cancel anytime, or $59 once for Pro Forever, and it unlocks every Pro theme, music sync, and every new theme as we release it. You can preview Reaction-Diffusion full screen before you buy: open the Themes panel and rest your mouse on it. Changed your mind? 14-day refund, no questions.

How to get it

1. Add Ambient New Tab to Chrome.
2. Open a new tab and click the Themes pill in the bottom-right corner.
3. Pick Reaction-Diffusion. Done.

Questions

Is this the maths behind animal markings?

Gray-Scott is one of the reaction-diffusion systems used to study how spots, stripes and maze patterns form in nature, the idea Alan Turing proposed in 1952. The two equations here are the standard Gray-Scott pair, with feed and kill rates that change as the front passes.

Is Reaction-Diffusion free?

It is a Pro theme. Pro is $5.99 a month or $39.99 a year, cancel anytime, or $59 once for Pro Forever. It unlocks every Pro theme, music sync, and every new theme as it is released.

Why does it never settle into a still maze?

A plain Gray-Scott run grows a labyrinth and then barely moves. Here the feed and kill rates keep changing behind a front that crosses the screen every 28 seconds, the whole field drifts on a current, and seeds keep landing, so some part is always reorganising.

Why are there no spirals or chaotic patterns?

Those Gray-Scott settings flood the screen with a flat sea of pink that reads as broken, so they are left out. Only stages that keep a dark background are used. The movement comes from the changes between them: a maze breaking into dividing spots, and spots stretching back into worms.

Does it work on my phone?

No. It's a desktop browser extension for Chrome on Windows, macOS, Linux and ChromeOS. If you're reading this on a phone, send yourself the link.

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