Funny: I have one prototype of it in my office at my university (but the sand has been removed) :-) Its code is from someone else I think... Ah, but mine does

Funny: I have one prototype of it in my office at my university (but the sand has been removed) :-) Its code is from someone else I think... Ah, but mine does an hydrological simulation on top of it (water flows in valleys). Besides that, these are super cool to show kids A.R.