I noticed that particles in powders dont react to water the way they would in the real world. I was going to mess around and make a geologic river simulation where I start the river have some particles like sand silicon dust at the top and watch them be transported by the water flow. When I set this up the particles didnt react to the water at all. I think it would be cool to see particles be moved and be pushed due to forces like running water. This would also open to alot more fun types of things for the community to make. Adding erosive featutres to rock and see solid break down into broken rock would be cool to see to. I know there are som simular powder games out there that have things like this in them they are normally limmited. I always like this powder toy better as it has had more options compared to others. In this aspect I always felt like there needed to be some growth on the physical interaction side.