Galton Box APP
The device is dropping "beans" from the top. For every row that a bean falls down, it has a 50/50 change of going either left or right.
This app simulates a Galton box, but it does it *very* fast. It can move millions of beans 60x a second or more (depending on your device). The simulation stops when the first bean hits the first column on the left. The stacks below the machine illustrate the number of beans that were dropped in each individual column. When enough beans fall down, the shape of the stacks approximate a normal distribution (also known as a Gaussian distribution or The Bell curve).
App also supports a "slow" mode, which just limits the number of beans to the number of CPU cores your device has. It makes it a bit more obvious, what's going on.