Reaching for food
The rule is local and greedy. Each growing tip looks at the nearby specks of food, leans toward their average direction, and extends a short new segment. When a tip gets close enough to a speck, that speck is consumed and gone. Pulled toward food on two sides at once, a tip forks.
Watch a single tip reach out, eat, and split — the whole network is just this, repeated.
It grows outward, and stays
Let the rule run across a whole dish of food and a venation network unfurls — forking, fanning, pushing toward the rim, where it splays into dense feathery fronts. Crucially the veins are permanent: nothing evaporates or drifts, the structure only ever accumulates. What you see is a record of everywhere the mold has reached.
Set the pace and watch it fill the dish.
Thick trunks, fine tips
Not every vein is equal. A vein near the centre must carry flow for everything downstream of it, so its width is the pooled width of all the tendrils it feeds — the pipe model. The result is the unmistakable look: bold arteries at the core thinning to gossamer at the fans.
Slide the taper to make the hierarchy gentle or dramatic.
Connecting the food
Scatter several piles of food and the mold grows out to reach them all, weaving veins between the sources — the experiment that famously reproduced a transport network. The branches that lie on the routes between food thicken into highways; the dead ends stay thin.
This adaptive wiring of points into an efficient network is the design payoff.
The Physarum studio
Grow your own. Click anywhere to drop a pile of food and the nearest veins reach out toward it, forking and thickening as they go; click again and the body extends further, never abandoning what it has built. This brainless, ever-accumulating network-builder — branching outward, pooling its arteries, wiring food into routes — is exactly the logic designers borrow for circulation, transport, and form.