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

A 3D fruit fly that lives on your macOS desktop - driven by a live spiking simulation of the real FlyWire connectome. It walks across your windows, grooms, sleeps, and decides to flee your cursor with the same neurons a real fly uses.

Brain window

The fly’s brain window shows 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 behavior

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 and setup

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.

Menu bar controls

Brain window interaction

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.

Behavior mapping

Body-to-brain loop

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 and rebuild

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

Tests and snapshots

./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.

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
• 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