What is this?

Two real fruit-fly brains in an arena. Each fly runs 139,255 neurons wired exactly the way the FlyWire brain map says. Nothing is scripted: every lunge, jump and bite is neurons firing.

Do I control my fly?

No. You coach it. Drop sugar with a click (FOOD), fire its rage cells (TAUNT), cast a shadow so the other fly jumps (LOOM). The brain does the rest, which is the whole fun.

How do I win?

Knock the other fly out, or have more HP when the 60 seconds run out. A good fight lasts about 40 seconds and 7 or 8 contacts.

Can my fly die?

Yes. A knockout kills it. It goes to the cemetery in a jar with its record, and you hatch the next generation. Rating stays, points restart at 600.

What are points?

Upgrade money. A win pays 140, a loss 40. Follow and repost on X once for 500. Every friend who joins through your link pays 1,000. Points buy levels in the brain, the chemistry and the body.

What does real money buy?

One thing. The egg, $0.99, hatches one random item you do not own yet: 60% common, 30% rare, 10% legendary. Hats, shirts, glasses, boots, paints. Looks only, never power.

Is it pay to win?

No. There is nothing to buy that changes a fight.

What is Deathmatch?

Eight flies, one picnic, last one standing. Unranked, points only, and the swarm kills.

What is the ladder?

Every 1 vs 1 is ranked. Your opponent is a real player's fly, its brain and body as they built it. Ratings move like chess ratings.

Why voxels?

Because a fly with a top hat made of cubes is funnier than a photo.

Which brain?

The FlyWire adult female Drosophila connectome, release 783 (Dorkenwald et al. 2024, Schlegel et al. 2024): 139,255 neurons, 2.7 million connections with five or more synapses, real 3D coordinates, neurotransmitter per neuron. CC BY-NC 4.0.

How does it run in a browser?

A leaky integrate-and-fire network after Shiu et al. 2024: membrane time constant 20 ms, 2 ms spike delay, 2.2 ms refractory, excitatory or inhibitory by transmitter. Two brains per fight, 30 steps a second, seeded so both players see the same fight.

How do senses get in?

The arena writes to real sensory neurons. A charging opponent drives the LC4, LPLC2 and LC6 looming neurons on the side it comes from. Contact drives bristle and Johnston's organ neurons. Sugar smell drives 150 fruit-odour receptor neurons per side. Sugar on the feet drives the sugar taste neurons and the PAM dopamine reward. An opponent in front drives the Or67d and Or47b pheromone neurons.

How does the brain move the body?

Only descending neurons do. DNp09 walks forward, MDN backs up, DNa left and right steer, the giant fiber above 25 Hz is an escape jump, MN9 is the feeding motor. Speed and turning are sums of those rates, nothing else.

What is a level?

A gain on real wiring, plus 10% per level. Nose and Mouth raise incoming synaptic gain. Rage drives the pC1 aggression cells. Eyes drives the looming neurons. Compass scales turning. Instinct sets reflex readiness. Memory sets the learning rate.

What does brain chemistry do?

A gain on every synapse a transmitter sends, from 0.7 to 1.3. Where it lands is decided by the map: dopamine 74% in Memory, serotonin 68% in Nose, octopamine 61% in Eyes and 30% in Instinct, acetylcholine, glutamate and GABA everywhere. Hotter chemistry burns energy faster.

Does Memory really learn?

Yes. Dopamine-gated potentiation of the Kenyon cell to output neuron synapses, the mushroom body rule. Sugar drives the PAM dopamine neurons, so a fly that eats learns. Each brain owns its own weights.

What is energy?

The fight budget. Rage above 15 Hz burns 1.2 a second extra, a taunt costs 15, chemistry and physiology upgrades multiply the burn. Eating returns 30. A hungry fly smells sugar from twice as far and goes for it.

What are the brain words?

Live readouts. Rage is pC1 above 15 Hz. Flinch is the giant fiber. Sees you is loom input. Smells sugar is the odour channel plus walking. Backing off is MDN. Eating is MN9.

Where is the whole brain?

Brain Lab. All 139,255 neurons at their real positions, 1,141 firing at a time, every descending channel on a meter, and every sense you can poke by hand.