Epidemic

An outbreak in a town of dots, against the SIR model. Flatten the curve.

0/2challenges

day 0

SusceptibleInfectedRecoveredSIR infected

Infection radiuspx

Chance per contact day

Illness lengthdays

Staying home%

Vaccinated%

Isolate cases once they have symptoms (day 2)

Population

Speeddays/s

Infected now: 0
Peak infected: 0%
Ever infected: 100%
R₀, estimated: 6.7
Herd immunity at: 85%

The model

Each dot is a person wandering a closed town. A susceptible person (blue) within the infection radius of an infected one (red) catches it with a set chance per day. Infected people recover (grey) after the illness length and are then immune.

The dashed lines are the SIR equations, dS/dt = -βSI and dI/dt = βSI - γI, with β estimated from how many people each person meets a day. The basic reproduction number R₀ = β/γ is how many people one case infects in a town where nobody is immune.

Try this

Flatten the curve: keep the peak under 15% with distancing or quarantine. Then find the herd immunity threshold, 1 - 1/R₀: vaccinate just above it and the outbreak fizzles; just below and it still spreads.

A toy model for intuition. Real diseases have incubation periods, households, ages and changing behaviour. Not a forecast. Educational model, not an engineering design or validation tool.

Achievements0/2

Flatten the curve +40End an outbreak with the peak under 15%.
Herd immunity +40Vaccinate past the threshold and stop an outbreak.

Biology
Flocking
Boids: three local rules, and a murmuration emerges. Chase it with a hawk.
Energy systems
Gridfall
Run a national grid with real DC power flow. A coach shows you how.
Physics
Falling Sand
Pour sand, water, oil, fire, lava and acid, and watch them react.
Cybersecurity
Blacksite
Incident response in a data hall. Real investigation, fictional hosts.

Try next

Flocking

Gridfall

Falling Sand

Blacksite