In this talk, we derive a simple 2D physics simulator, focusing on gravity and spherical objects. The speaker walks through a basic introduction to Newton's laws, and then derives a formula for a discrete approximation of the equations of motion. We convert the discrete approximation of the equations of motion into Ruby code, which accepts a state at a particular time, along with an interval of time, and then computes the new state at that following time interval. This updated state is then rendered using an HTML5 canvas element. The talk concludes with some demonstrations involving randomized initial conditions, highly symmetric initial conditions, and some awesome 3-body stable orbits.