A simple HTML5 canvas particles collision detection animation, which explains the importance of stay home and avoid social contact.
Basically, 100 people (particles) is put on the screen, with 1 person getting infected initially. When the infected people interacts with those healthy people, COVID-19 starts to spread. You can put people under quarantine and they will stop moving.
I am thinking of introducing other interesting mechanisms like death rates, hospitalization to this simulator.