The N-body problem is the problem of finding the motion of a group of particles that are all acting on each other, for example through gravitation. A nice summary can be found here: https://en.wikipedia.org/wiki/N-body_problem.
Instead of attempting to solve the six differential equations required to accurately find the motions of these particles, we can approximate it with discrete time steps. This is my attempt to do so in javascript using three.js for visualization.