Falling sand experiments have been continuing. I have now basically a working engine which supports currently

- static ground and grass

- sand, snow water and "gas/vapour" particles

- freezing / melting between water<-> snow

- water boiling to gas (due to fire)

- fire particles

- every pixel is simulated :)

- scrolling map where all of the above can happen. Screenshot below, with "progammers art" :)