Drag on the picture to lay food: the agents gather to it. The address of the page keeps the settings, to share them.
A brain without a brain
Physarum polycephalum, the many-headed slime mold, is a single cell that can grow to the size of a plate. It has no brain, yet it finds the shortest path through a maze, and in 2010 researchers in Japan watched it rebuild the Tokyo rail network: oat flakes placed at the cities, it linked them with veins as efficient as the engineers' tracks.
The same year, Jeff Jones showed how such networks can emerge from very simple agents. Each one walks forward, sniffs the trail ahead, a little to the left and a little to the right, turns toward the strongest scent, and leaves a bit of scent where it goes. The scent spreads and fades. Nobody draws the veins: they appear because every agent follows the others.
Change how far and how wide the agents look, and how sharply they turn, and the network changes character: long trunks, fine lace, wobbling cells, crawling worms, or, when they turn away from the scent, a foam of dots. Drag on the picture to lay food, and watch the mold reroute itself to reach it.