2D Sand Automaton

This is the flat, pixel-grid companion to the 3D Sand Automaton: the same falling-sand cellular-automaton idea, drawn directly as a 2D material grid instead of projected onto a WebGL texture. Sand, water, wood, fire, stone and wall cells each carry their own local update rule — sand slides to its angle of repose, water seeks the lowest open space, fire consumes and spreads through wood while water puts it out, and stone and wall sit immovable underneath everything else. Paint with any material and watch the same handful of rules produce piling, pooling, burning and settling behaviour purely from cell-to-cell interactions.