Experiment 001
Evolution Tank
A tiny ecosystem nobody controls. Creatures with untrained neural-net brains eat, breed and mutate on their own. Watch slugs evolve into spiky grazers, a predator branch split off, and whole populations boom and crash.
Field notes 0:00 sim time
Hall of Fame
Champions are saved in this browser and shared by all your tanks. Release one to drop an exact copy of its brain back in, or Share it as a link a friend can open.
Readouts
Population
Brain scan leader
Tap a creature to scan its brain. Amber wires excite, blue wires inhibit. Faded creatures are starving. Predators have jaws, stripes and red eyes, and sense prey where prey sense food. Blue rings are births, red bursts are kills.
Controls
Your tanks
Tanks save themselves every 30 seconds and whenever you leave the page. They live in this browser only. New tank keeps this one here.
Leaderboard
See all →Loading the leaderboard…
Entries go up after a quick check that replays your tank from its seed. Submit again any time to update your entry.
How the Evolution Tank works
Every creature has a brain: a tiny neural network with 9 inputs, 8 hidden neurons and 2 outputs. The inputs are what it can sense, such as the direction and distance of the nearest food, the nearest predator, a wall ahead and its own energy. The outputs steer it: how hard to turn and how fast to swim.
Nobody trains these networks. The first creatures get random wiring, so most of them spin in circles and starve. A few bump into food by luck. Eating stores energy, and a creature with enough energy has a baby that inherits a slightly mutated copy of its brain, sometimes mixed with a nearby mate’s.
Over many generations, the brains that survive are the ones that steer toward food and away from danger. That’s natural selection, and evolving neural networks this way is called neuroevolution. Tap any creature to open its brain scan and watch the wiring that evolved.
Predators, prey and the boom-and-bust cycle
Once a family line has survived long enough, one of its babies can be born a predator. It keeps its parent’s food-seeking brain, but now senses other creatures instead of algae. From then on the two branches evolve against each other: hunters get better at chasing, and prey that react to danger live longer.
Predators only breed when they eat well. When they eat too many prey, they starve, and the prey recover. The rise and fall of the two populations on the chart is the classic predator-prey cycle that ecologists describe with the Lotka-Volterra equations. Nothing in the code tells the populations to cycle. It emerges from hunger and reproduction.
Things to try
- Run at 16× for a few minutes to skip past the early die-off and reach the first predators.
- Press Follow predator and watch a hunter chase prey in the close-up camera.
- Set the mutation rate to 1% and then 40%, and compare how fast the tank evolves.
- Release a Hall of Fame champion into a fresh tank of slugs and see whether it takes over.
- Open the Field guide and try to spot every stage, including the rare apex predator.
- Press New tank to start fresh. Your current tank waits under Your tanks, so you can switch back any time.
- Send a friend a Hall of Fame champion with Share and see how it does in their tank.
- Grow a deep lineage and press Submit this tank to get on the leaderboard.
The stages of evolution
- Slug, eyespot, swimmer: the early prey, growing eyes and a tail fin.
- Finned, feeler, spiker: later prey with side fins, antennae and dorsal spikes.
- Stalker, ripper, apex: the predator branch, with stripes, jaws and red eyes.
A creature’s body shows how many generations its family line has survived. Its brain evolves separately and decides how it actually behaves.
Frequently asked questions
Is this real evolution?
It’s a simulation of the same process: random variation, inheritance and selection. Creatures that find food reproduce and pass on their brains with small mutations. Nothing is scripted, so every tank evolves differently.
Are the creatures trained with AI?
No. There’s no training step. Each brain is a small neural network whose wiring is random at first and changes only through mutation when a creature has a baby. Better brains spread because their owners survive.
Why do predators appear?
Once a prey family line reaches the swimmer stage, each baby has a small chance of being born a predator. If that new hunter catches enough prey, it founds a whole predator branch.
Why do the populations crash?
Prey are limited by how fast algae grows, and predators are limited by how many prey they can catch. When either group outgrows its food, many starve, and the cycle starts again.
Does it save my tank?
Yes, in this browser. Your tank saves itself every 30 seconds and whenever you leave the page, so you can close it and pick up later. New tank keeps the old one under Your tanks. Saved tanks stay in this browser only and are never sent to a server.
Can I share my tank or a champion?
Yes. Share this tank makes an image of your tank and its stats that you can post anywhere. In the Hall of Fame, Share gives you a link to a champion, and whoever opens it can release an exact copy of its brain into their own tank.
Is there a leaderboard?
Yes. Press Submit this tank and your tank’s records go on the Evolution Tank leaderboard: deepest lineage, longest predator line and greatest champion. Every entry is checked first by replaying the tank from its seed, so the numbers are real. Only family lines that evolved in your own tank count, not champions released from somewhere else.
Does it work on phones?
Yes. The tank, camera and controls all work on a phone. Tap a creature to scan its brain and use the buttons to change speed and camera.