Pick a system and push on it.
Each simulation is a working model. Start from one of its questions, or just move a slider.
Traffic World
Traffic Ring
Buses circle a 25 km route, one every eight minutes. Let a stop get busy, or a light hold one bus, and watch an even timetable turn into long gaps and bunches of buses arriving together.
Traffic World
Phantom Jam
Dozens of cars share a closed road. One brakes hard, then drives on, and the slowdown it started runs backwards through the traffic with nothing in the way.
Traffic World
Green Light
A four-way junction with left-turn arrows and amber lights. When a light turns green, how quickly the waiting queue sets off decides how many cars get through.
Nature World
Predators & Prey
Foxes hunt rabbits across a meadow. Every animal is an individual that eats, breeds, starves or gets caught. Tap one to follow it, change the rules, and watch the populations boom, crash or disappear.
People World
How Rumours Travel
A small town hears something. Follow it for a whole year: who tells whom, how the story changes, which version wins, and how it ends. There are 9,999 different stories.
People World
How Smoking Hooks the Brain
Follow one person from a first cigarette on a night out, through getting hooked, to the day they try to stop. Watch nicotine fit into the brain, the need grow, and the habits that keep pulling.
Physics World
Collision Lab
Carts, pool balls, curling stones, cars and bowling balls collide on a track. Change the masses, speeds and bounciness and follow where the momentum and the energy go, collision by collision.
Economy World
Inflation
Prices drift upward month by month. Watch four neighbours and a bank on one street: who gets squeezed first, who gets caught out by a rent renewal, and what a central bank can do.