0 rabbits 0 foxes 0 hunters 0% grass herding 1.00 0 minnows 0 pike order 0 0:00 1× real 60 fps

Click to place · drag to move · shift-click to remove · scroll to zoom · Space pause · G rig · P drive

Procedural predators

Nothing here is a sprite sheet or a canned animation loop. Every pose is solved on the frame it is drawn: a spine dragged behind the head, feet that stay planted until the body has left them behind, and tails and ears that are just mass on a spring. Change how something moves and the way it looks moving changes with it, because there is nothing else for it to fall back on.

Start from

Then try

A scenario lays out the population and the ground as well as the settings; the second row perturbs whatever is already running. Both change the link in the address bar, so anything you find is something you can send on.

Place

Inspector

Nothing selected

Click a creature to inspect it.

Energy Stamina

While driving: W run, A/D turn, Shift crouch. You get the same turn-rate limit the brains do.

Populations

caught 0 shot 0 starved 0 born 0

per minute over the last minute; totals for the whole run in brackets

Simulation

Time Turbo Pace Sight Crypsis Regrowth Accuracy

Breeding Hunting

Evolution

Each animal also inherits a small neural network, crossed over from both parents and mutated. Nothing trains it — a network only spreads because the animal carrying it lived long enough to breed. Learned dials how much of each decision comes from that network rather than from the hand-written instinct; at 1.0 the founding generation genuinely does not know what a fox is.

Every animal carries six heritable traits, each starting at 1.0. Nothing selects on them directly — a rabbit with longer legs takes longer strides, so it escapes more foxes, so it breeds more often. Traits cost metabolism, so none of them simply runs to the maximum.

rabbit gen 0 fox gen 0

Under selection now

How far the rabbits that died sat from the average living rabbit. A trait mean drifting upward proves nothing on its own — small populations wander. This does: a negative figure against eaten means the animals with less of that trait are the ones being caught, so it is being selected for. Predation and hunger pull opposite ways, and a trait settles where they balance.

Mutation Step size Learned Arrivals

Inheritance

Tank

Three local rules and nothing else: keep off your neighbours, match their heading, drift toward them. No fish can see the school it is in — every fish sees a few neighbours inside a blind-spotted cone. Invert any two weights to watch it fall apart.

Separate Align Cohere Vision Fear Current

eaten 0 born 0 gen 0

Evolution

Fish inherit on the same terms as the rabbits do: six traits and a small network, crossed from both parents and mutated. Nothing is trained — a brain spreads only because the fish carrying it lived long enough to breed.

Learned Mutation Step size Arrivals

Inheritance

Animation

Every one of these was a constant chosen once and buried in the species table. They are multipliers on each animal's own value, so 1.0 is as-designed and there is always a way back. Changes reach animals already on screen — nothing snaps to a rest pose.

View

Wind Blades Volume Zoom

Grass Who can see me Weeds Caustics Follow selection Show every rig

Every sound is synthesised — there are no audio files here either. Footfalls fire from the gait solver's own foot-plant events, so a gallop has a gallop's rhythm because it is one, and retiming the swing on the Animate tab retimes the sound with it. Muted while fast-forwarding, since a minute of hoofbeats inside one second is not a sound.

Select or drive a creature and every animal that can currently perceive it draws a line back to it, fading with how strongly it has you. Predators get a solid line and a filled cap. Stop moving, or get into deep grass, and watch them let go one at a time — that is the whole stealth model, which is otherwise invisible.

The rig overlay draws the spine joints, each hip, and a dashed line from every foot to where it would rest if the body stopped. A step fires when that line gets too long — which is the whole of the walk cycle.