fruitflyworld / sim

The simulation core of fruitfly.world — the dish world, the escape circuit, and a slot for a brain.

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Zero dependencies. Zero build. Plain ES modules that run in the browser and, unchanged, in Node 22 — the same files the live game at fruitfly.world/play executes in production. This repository is the source of truth for the numbers; the game vendors these files.

What is in here

Module	What it holds
js/sim.js	The deterministic dish world: seeded RNG (makeRng), the mutation draft (draftCards, draftSeed), the escape assay and the real-vs-swapped wiring check (runExperiment)
js/dmath.js	Deterministic math kernels: dsin/dcos/dexp/datan built only from IEEE-pinned operations, because Math.sin/cos/exp/atan differ in the last ulp across CPU architectures (~3%–5.6% of inputs, arm64 vs x64). The sim lane runs on these; render code may keep Math.*
js/world.js	The whole autopilot lane as a pure Node module (runLineage): food, predator, drafts, brains, generations — no DOM, no Phaser, byte-faithful to the browser including its cross-generation artifacts. WORLD_VERSION tracks world semantics (currently dish/3)
js/gf-neuron.js	The brainstem: a leaky integrate-and-fire Giant Fiber driven by LC4 (angular velocity) and LPLC2 (looming) — the two visual neurons that dominate the real fruit fly's escape command cell
js/cx-circuit.js	FFW-CX/0.1 — a 24-neuron spiking circuit with connectome-inspired structure. All randomness is at construction time, which is what makes it examinable
js/brain.js	The brain contract: signals in → behavior distribution + confidence out, every decision sealed with a FNV-1a contentHash
js/brain-circuit.js	Wraps FFW-CX into the brain contract
js/brain-local.js	A free local heuristic brain — the default judgment layer
js/brain-jev.js	A System One-compatible judgment brain: pinned model, same-origin proxy, hard-fails on floating aliases
js/brain-driver.js	The metronome: steps synchronous brains on a clock, lets async brains fly solo, expires and drops stale answers, flags degradation

Each .js ships with a sibling .d.ts.

The pinned numbers

These are not aspirations; they are assertions. npm test (38 tests, Node 22's built-in runner — no install step) fails if any of them drift:

Fact	Value	Source
Real connectivity escapes telegraphed lunges	100% of 200 (runExperiment(1337))	tests/gf-neuron.test.ts
Swapped connectivity escapes	68% of 200	same wiring check, same seed
FFW-CX behavior trace, seed 42	contentHash = 9fb9e0d0	tests/cx-circuit.test.ts
FFW-CX hunger assay, bucket 1	274 of 300 ticks	tests/cx-circuit.test.ts
Mutation draft golden vector	contentHash = 0f4d39c3	tests/sim-cards.test.ts
Rival genes, seed 1337	contentHash = e9b1d202	tests/sim-cards.test.ts
Escape trial seed 12345, real	{escaped: true, lead: 0.1833…}	tests/gf-neuron.test.ts
60-case golden baseline vs world.js	1260/1260 field checks identical (3 brains × 20 seeds × 3 gens, arm64 Chrome vs x64 Node)	tests/world-parity.test.ts + tests/golden/baseline-dish3.json

The 100/68 pair is a simplified two-channel wiring check, not a control experiment on the connectome: within this model, real-beats-swapped holds by construction, and the escape rates are a function of hand-set parameters. (The code identifier stays "shuffled" — the pinned golden vectors hash it.)

Use it

import { makeRng, draftCards, makeGFState, runExperiment } from "./js/sim.js";

runExperiment(1337);          // { n: 200, realEscape: 100, shufEscape: 68, ... }
makeRng(42) === makeRng(42);  // same seed, same sequence, forever

import { createCircuitBrain } from "./js/brain-circuit.js";

const brain = createCircuitBrain(42, 100);       // seed, interval ms
const record = await brain.decide({              // the whole brain contract
  tick: 0,
  signals: { food: 0.7, threat: 0.1, light: 0.5, novelty: 0.2 },
  energy: 60, timeLeft: 40,
});
// record.behavior, record.confidence, record.distribution, record.contentHash

The brain contract

Above the brainstem, everything is a slot. A brain is anything that fulfills one contract: given four signals (food proximity, threat, light, novelty), energy and a clock, return one behavior (approach / avoid / explore / freeze) and a confidence. The brain chooses; the brainstem jumps — the escape reflex is not pluggable, because that is the biology the project is built around.

Honest boundaries

• The circuits are connectome-inspired, not simulations of a real fly brain, not FlyWire or MaleCNS runtimes, and not claims about animal behavior.
• One seed is one row of a table, not a theorem.

Related repositories

Repository	What it holds
fruit-fly-world	The full site: game, exam room, missions, Passport contract
game	The playable game (Phaser), with this core vendored
bench	The reproducible double-run exam harness

Vulnerabilities are reported privately through the main repository's security policy, not in public issues.

License

MIT © 2026 Fruit Fly World