# A 3D fruit fly on macOS desktop powered by the real FlyWire connectome

> Source: <https://github.com/DenisSergeevitch/desktop-fly>
> Published: 2026-08-18 21:50:33+00:00

A 3D fruit fly that lives on your macOS desktop — driven by a live spiking
simulation of the real [FlyWire](https://codex.flywire.ai)
connectome. It walks across your windows, grooms, sleeps, and decides to flee
your cursor with the same neurons a real fly uses.

The fly's brain window: 23,210 real neuron soma positions from FlyWire v783,
with live spikes flashing at real neuron locations. The two glowing yellow
markers are the Giant Fibers — the escape command neurons. Click any region
to stimulate it.

**23,210 neuron soma positions**(of 139,255 in FlyWire v783) render the rotating brain window, colored by super-class (FlyWire's coarse cell-type grouping).**A 668-neuron circuit with ~19,000 real synaptic connections**(synapse counts, signed by neurotransmitter prediction) runs as a 1 kHz leaky-integrate-and-fire (LIF) simulation:** LC4 (104) + LPLC2 (210)**looming-detector visual neurons** DNp01 / Giant Fiber (GF) (2)**— the escape command neuron** DNa01 + DNa02 (4)**steering neurons ·** DNp09 (2)**forward walking** DNg11 (6)**grooming ·** MDN (4)**backward walking ("moonwalker")** DNp02/DNp04/DNp11 (6)**escape-maneuver (wing) neurons- their 330 strongest partners, including ascending (proprioceptive) and sensory (wind) neurons

**Escape is not scripted.** Your cursor's approach becomes looming input to the real LC4/LPLC2 cells; the fly takes off only when the Giant Fiber actually spikes through its real synapses — ~1,200 synapses of feedforward inhibition push back, which is why slow approaches are tolerated and fast lunges trigger escape in ~4 ms, just like the real animal.

The body itself is procedural (FlyWire is a brain connectome — no body geometry exists), with a tripod gait, visible wing-beat, altitude-scaled flight, grooming, and sleep postures.

Requirements: **macOS 13+**, Xcode Command Line Tools (Swift 5.9+).
No permissions or entitlements needed — everything it senses
(cursor, window frames, clicks-as-taps, thermal state) is permission-free.

```
git clone https://github.com/DenisSergeevitch/desktop-fly.git
cd desktop-fly
./build.sh
./DesktopFly
```

A 🪰 item appears in the menu bar; quit from there. The fly wanders your desktop on a transparent, click-through overlay — it never intercepts your mouse or keyboard.

| item | effect |
|---|---|
| Pause / Resume | freeze the world |
| Show/Hide Brain | toggle the live brain window |
| Escape Test (loom) | inject a looming stimulus, watch the GF fire |
| Move to Next Display | hop the fly across monitors (shown when >1 display) |
| Add / Remove Fly | extra flies (only fly #1 carries the brain) |
| Scare Flies | startle everyone |

**The brain window is interactive**: hovering pauses the rotation; clicking a
region "optogenetically" stimulates the ~60 nearest circuit neurons for
400 ms. The fly's reaction is whatever the real network does downstream —
click the Giant Fiber and it escapes; click DNg11 and it grooms; click one
side's DNa01/02 and it turns.

| body behavior | driven by |
|---|---|
| escape takeoff | DNp01 giant fiber spike |
| walk vs. rest, walking speed | DNp09 rate |
| steering | DNa01+DNa02 left−right rate difference |
| grooming | DNg11 rate |
| backward scoot | MDN burst |
| nervous darting | LC4/LPLC2 population rate |
| wing-beat effort, threat wing-raise | DNp02/04/11 rate |
| spontaneous takeoff | whole-population arousal |

The loop also closes body→brain: the gait rhythm feeds the circuit's real ascending (proprioceptive) neurons in phase with the legs, and fast cursor motion stimulates its sensory (wind) partners.

**Window terrain**: window top edges are ledges — the fly lands on them, walks along them, rides a window you drag, and startles when one closes under its feet.**Window looms**: a window appearing near the fly feeds the looming pathway; the circuit decides whether to flee your dialogs.** Clicks are substrate taps**; clicking next to the fly startles it through the wind→GF pathway.** Typing is vibration**(idle-time API — knows*when*keys were pressed, never which).**Circadian rhythm**: dawn/dusk activity peaks, midday siesta, night quiescence.** Sleep**: idle at night → it sleeps, breathing slowly, with raised arousal threshold; it grooms after waking.** Temperature**: flies are ectotherms — a hot Mac is a faster fly.

`data/`

ships with compact derived files. To rebuild them from the raw
FlyWire Codex dumps (~60 MB download):

```
mkdir -p /tmp/flywire && cd /tmp/flywire
B=https://storage.googleapis.com/flywire-data/codex/data/fafb/783
curl -O "$B/classification.csv.gz" -O "$B/coordinates.csv.gz" \
     -O "$B/connections.csv.gz" -O "$B/consolidated_cell_types.csv.gz"
cd - && python3 etl.py /tmp/flywire
./DesktopFly --simtest        # circuit invariants: GF silent at rest, 4 ms loom latency, ...
./DesktopFly --behaviortest   # 17 end-to-end checks: stimulate neurons -> body reacts
./DesktopFly --snapshot f.png  # offscreen fly render
./DesktopFly --brainshot b.png # offscreen brain render
```

Honesty section: the connectome gives wiring, not physiology. The LIF dynamics, neurotransmitter signs (ACh+, GABA−, Glu−), the gap-junction boost on LC→GF and wind→GF (documented electrical coupling), synaptic delays, and the sensory transduction (cursor → looming value) are standard modeling choices layered on the real graph. Everything downstream of the sensory neurons — who connects to whom, and how strongly — is FlyWire data.

Code is MIT. The files in `data/`

are derived from FlyWire (FAFB v783) and
are **CC BY-NC 4.0** — see [data/DATA_LICENSE.md](/DenisSergeevitch/desktop-fly/blob/master/data/DATA_LICENSE.md).
If you use this, cite:

- Dorkenwald, S. et al.
*Neuronal wiring diagram of an adult brain.*Nature 634, 124–138 (2024).[https://doi.org/10.1038/s41586-024-07558-y](https://doi.org/10.1038/s41586-024-07558-y) - Schlegel, P. et al.
*Whole-brain annotation and multi-connectome cell typing of Drosophila.*Nature 634, 139–152 (2024).[https://doi.org/10.1038/s41586-024-07686-5](https://doi.org/10.1038/s41586-024-07686-5)