I wrote this to do a play with a few ideas, but largely because I saw a Washington Post article that did some simulation of COVID-19 infection rates. I wanted to be able to play around with some of those settings (and add more later), so here we are! Change up the settings and press start. The lower image will show the progression of infections and the simulation will stop automatically when there are no more infected balls. The URL updates automatically with your settings so you can share your particular epidemic!

Press Start to simulate!

I realize this whole thing could be a bit morbid, but I think it's an interesting visual way to show the spread of anything contageous and some factors that spread might be dependant on. Here are some examples:

- Pessimistic COVID-19 - A mortality rate of about 5%, highly infectious, no social distancing. We end up with virtually everyone sick at the same time at some point. This is what social distancing is trying to avoid.

- Social Distancing COVID-19 - If about half of us limit our mobility, it slows the spread of the disease dramatically. Over time, everyone still gets sick, but the total number of sick people at any one time is far smaller. Something (hopefully) hospitals can handle!

This can also be used to look at herd immunity!

- Measles, "low" herd immunity - With something highly infectious, even when we as a group already have 80% immunity, it still spreads throughout the entire population.

- Measles, high herd immunity - Depending on the simulation, this time it may die out on its own, or may spread, but very slowly, giving the opportunity to use tools like quarantining of individuals (who have to present symptoms and be detected first). Increase to 95% immunity and you'll see that most of the time, it dies off on its own, with no action required.

And if you're just in for an elastic collision simulation, here you go.

Please note, none of these scenarios are "real", it's just a model simulation with estimated values. This is a toy, not a scientific tool.