The procedure is very simple, with surprising results, and is used to represent fluids in video games . It is based on the fact that the wave equation (a second-order PDE) can be rewritten as a system of two first-order PDEs
for which a possible discretization is
An implementation with some variations can be found at , with an updating scheme is based on : given two arrays, for the time and representing . From an element in , the sum of the four neighbors that appear in the discretization of a component in is subtracted, giving an updated value for , with the exception of positions at the walls. A CFL constant (Courant–Friedrichs–Lewy condition) is necessary to ensure stability.