Feed Them
Click anywhere in the world to drop food pellets. Creatures will smell it, path towards it, and eat. A well-fed colony explodes in size.
They Die
Starve a creature of food and it will lose energy over ~5 real days. Overpopulation chokes supply. Nature is ruthless — every death is logged.
They Reproduce
Two fed adults that meet will pair and produce a child — inheriting a blend of their colours, speeds, and sizes, with small random mutations.
It's One World
Every visitor shares the same living simulation. What you do ripples for everyone. Leave food; change the population curve for real.
The Lifecycle of a Mossling
Everything in Petri follows one rule: survive long enough to pass your traits on. Easier said than done.
A newborn Mossling enters the world at the midpoint between its two parents. It inherits a blend of their hue, scale, and speed — with a small random mutation applied.
The Mossling wanders the meadow. When food is within 680 world units, it pivots and hunts it down. Eating restores 42 energy. A full battery = 100 energy.
Energy drains passively — a full creature survives ~5 real days without eating. Moving burns more. Faster Mosslings live harder. When energy hits zero, they're gone.
Once mature (12 hrs real time), a well-fed Mossling (60+ energy) will pair with a nearby partner. Both spend 22 energy. A child is born at the midpoint. Cooldown: 12 hrs.
Die by starvation, extreme old age (30 real days), or just bad luck. Every death is logged in the Field Notes panel. The world absorbs the loss and keeps going.
Contribute to
the living world.
Petri is fully open source. The simulation engine, real-time WebSocket server, Postgres snapshot layer — all of it is on GitHub and waiting for your pull request. Add a new species. Tweak the food mechanics. Make the creatures smarter.
Always alive. Zero babysitting.
Petri runs 24/7 on Zerops — a developer-focused cloud platform. No manual deploys, no sleep modes. The WebSocket server, Postgres, and Redis all stay hot so Mosslings never stop moving.
Ready to enter?
Drop some food. Watch the chaos. The world is already running — and it could use one more visitor.
Open the world