Who is the fly?
In 2024, scientists on the FlyWire project finished mapping every connection in an adult fruit fly's brain: about 140,000 neurons and 50 million synapses. It was the first complete wiring diagram of an adult animal's brain at that scale.
In 2026, Carlo Esposito turned that map into a chess player. The wiring is exactly the fly's. Which neurons connect, and whether each connection excites or calms the next neuron, never changed. Only the strength of each connection was trained.
The board goes in through the fly's sensory neurons. Its move comes out of its motor neurons. It learned from 58 million positions played by strong online players, then practiced against itself.
The result plays sensible openings and misses tactics. Its creator calls it a weak chess player. That makes it a fair, and very strange, sparring partner.
Super Fruit Fly is the fly with an engine boost. It still weighs in on every move, but Stockfish, the strongest open-source chess engine, makes the final call, held to a 2500 rating. It is built for coaches and strong players.
FlyWire connectome (Dorkenwald et al., Nature 2024). Chess model: fly-chess by Carlo Esposito, CC BY-NC 4.0. Super Fruit Fly engine: Stockfish.js 19, GPLv3. For fun, not for sale.