The simple applet on this page shows a cellular automata model of the deposition of metal particles (red blocks) onto a metal substrate (black block) as might occur during electroplating. The background electrolyte is blue.
An electric field (value 0-1) biasses metal particles to move downwards, while the presence of an impurity (or leveller) with with the given concentration will affect the deposition of the metal at the surface. The leveller particles can "unstick" the metal particles from the surface on contact with a given probability.
The simulation will run until "end-time", or until the pause button is clicked. The end-time can be increased while the simulation is paused. Click "Reset" then "Start" to start a new simulation with new parameters.
Metal particles enter at the top with probability 0.03 each timestep, Levellers likewise, except the probability can be set. Both can diffuse out of the top, the sides have periodic boundaries.
Notice how adept the levellers are at compacting the deposit, and not themselvesgetting trapped.