A vectorised sandpile class. The sand piling game consists of the driving a system by adding a grain to a cell, typically the orgin. These grains pile up. Eventually they fall over if they get too tall (4 grains) and send one grain to each neighbouring cell. Gradually the grains spread out in a symetric and circular pattern.
It should run up to 1e5 grains fairly quickly. Make sure the grid size is appropriate (i.e n * n * 4 at a minimum)