Harena vs MyFly World

- 165 materials: sand, water, lava, acid, metals, gases, plants, creatures. 32 of them are made only by reaction - Grids up to 2048 x 1152, 2.36 million cells, every cell simulated - Heat: every material has a melting, boiling and ignition point, and latent heat - Reactions have a temperature window, and each one you find is logged in the codex - Four views: material, thermal, velocity and air flow - Electricity: wire, battery, diode, lamp, and heat, cold and wind sensors - Optics and magnetism: laser, mirror, prism, two magnets, pump - Wind and pressure: smoke, spores and ash are carried by the air - Creatures and vehicles, including a character you steer yourself - Six starting worlds, ten save slots, undo, pinch to zoom and pan. Landscape only, playable offline

This is not a virtual pet that behaves "like" a fly. It is a real fruit-fly brain: 139,255 neurons and 2.7 million synaptic connections from the public FlyWire whole-brain connectome, spiking millisecond by millisecond on your phone. Every turn, pause, grooming bout and feeding you see is computed by that real neural network. You never steer it. You change its world. Drop the brain into a scout drone, a patrol car, a six-legged worker or a rolling probe and it explores on its own. You walk the cyber laboratory in first person: place a lamp and it comes to the light; place an apple (or a dropping) and it follows the smell; switch on a fan, put down sugar water, press a buzzer, shine your torch at it. Every sense is wired to the fly's real sensory neurons, and the reaction is its own. The arena wing Put the same brain into a small fish in a tank with piranhas, or into a beetle, a mantis or a crab facing a wasp in the colosseum. The mantis strikes only when its front feelers are touched, the crab pinches on the side that gets pressed, the beetle never fights back but has a shell. You control the tank lamps, the bait, the tapper, the bell and the opponent settings, then watch how long it lasts. Up to three brains at once The incubator grows three complete brains; each one gets its own body and lives independently. Honesty is the design rule The screen always shows what its two eyes see, what its nose smells, which descending neurons are firing and how many milliseconds the reaction took. The notebook states, entry by entry, which behaviours come from the neural network, which are declared body reflexes and which are environment rules. It cannot learn, has no motion vision and no emotions, and the app says so. Technology FlyWire FAFB v783 connectome, the Shiu et al. 2024 leaky integrate-and-fire model, all neurons computed on the GPU. Works offline. Collects no data.