Every dot on screen is an agent. It sniffs the ground just ahead of it, turns toward whatever smells strongest, walks a step, and leaves a bit of scent behind. That's the whole rulebook. Nobody draws the veins — they're what a million agents following each other's scent end up agreeing on.

Eight ready-made colonies. Each one just sets every slider in the other panels to a different recipe — a good place to start before you go fiddling.

How one single agent decides where to walk next.

How far out to the sides it can see. Narrow and it mostly stares straight ahead, so it commits to long smooth veins. Wide and it keeps noticing trails off to the side, so it doubles back and knots up into tangles.

How far ahead it can see. This is the big one for scale — short sight gives you fine lacework, long sight gives you a few huge sweeping shapes.

How hard it can swerve once it smells something it likes. Low is a lazy drifting curve; high is a sharp, twitchy correction.

How far it walks each tick. Big steps make a restless, coarse, fast-moving colony that can outrun its own trail.

How much it ignores the rules and goes its own way. A pinch keeps things organic and stops the pattern freezing. Too much and it dissolves into fuzz.

The scent itself — the stuff they leave behind and then follow. This is the colony's shared memory, so these three decide how long a good idea sticks around.

How much scent each agent drops as it walks. More means trails shout louder, so agents commit to them harder and the veins get bolder.

How much scent survives each tick. Around 0.90 it evaporates fast and you get thin, restless, constantly-rerouting lines. Near 0.99 it lingers and the colony settles into thick permanent roads.

How much the scent smears outward into the ground around it. Low keeps crisp hairlines. High makes it soft, spreading and blobby — and lets agents find trails they'd otherwise walk straight past.

How many rival colonies share the dish, each with its own colour. They start out holding separate patches of territory.

How much they hate each other's scent. At 0 they ignore each other and mingle freely. Turn it up and they carve hard dark borders. Turn it too far and they scrub out each other's trails faster than they can lay them, and everything fades away. Only does anything with 2+ species.

How many agents are alive. More agents means finer, denser, more detailed webbing — not a brighter picture, since the scent is toned down to compensate. Drag this down if your laptop fans spin up.

How fast time runs. Higher grows the pattern quicker but asks more of your GPU each frame.

Where everyone stands at the very beginning, before they organise. Picking one restarts the colony. The opening shape leaves fingerprints for a surprisingly long time.

Scatters everyone again and wipes the scent — same settings, fresh run, different result every time. Anything you've put on the dish stays put.

Drop something on the dish and watch what the colony makes of it. These aren't walls — they're smells, and they reach a long way. Agents weigh them up exactly the way they weigh up each other's trails, so nothing here is scripted: the network you get is the colony's own answer.

oat flake — food, and the reason this organism is famous. Agents pile in, and the traffic between flakes thickens into proper trunk routes.
salt — harsh and close-range. They refuse to cross it, so it cuts the dish into rooms and the network has to find the doors.
light — mild but very wide. Physarum creeps away from it, so it herds the colony rather than blocking it.

Tap the picture to put one down. Tap it again to take it away.

How loudly any of this registers next to the scent of their own trails. At 0 they can't smell it at all and you're just decorating. Push it up and the substances win every argument.

Nothing on the dish yet.

Pick one, then drag anywhere on the picture to meddle with the colony while it's running.

attract — bend agents toward your cursor, like a light.
repel — shove them away and tear a hole open.
feed — smear fresh scent on the ground; they'll come running and build there.
erase — wipe trails out and let them start over.

Size of the area your cursor affects.

Pure paint — none of this changes what the colony actually does.

Colour scheme. With several species, each one takes a colour from the set.

Overall brightness. Push it up to find faint trails hiding in the dark; pull it down if everything's blown out to a flat glare.

How harsh the gap is between the bright veins and the dark gaps.

How much light bleeds off the veins into the dark around them, the way a bright thing blooms when you photograph it. At 0 you get the bare data, crisp and clinical. A little makes the network feel lit from inside; a lot drowns it in haze.

Writes the picture as you see it, without any of this furniture, to your downloads.