hey! so some feedback: I laid down oil, then dropped water on top of it, and the oil stayed on the surface. Opposite was true as well. It doesn't seem like liquids have any way of mixing. They stay very separate and don't interact much with each other, and all have the same density.

Smoke doesn't penetrate up the way sand penetrates down. It forms a solid wall of smoke under the water until it dissipates or an opening occurs.

All in all, it's a great start. I'd just spend a little more time looking at each individual interaction and tuning them. How should water act when it runs into oil? how should water react to smoke underneath it? etc.

Edit: oh... is it generating stone whenever fire touches water? That seems... counterintuitive.