Hi, I am a total noob which seems to be a terrible insult on this forum, but I prefer to announce the colour.
I downloaded Powder Toy after OE-Cake! and this is quite an interesting experience. At least Powder Toy has a living community while I couldn't find on OE-Cake!.
I am not anymore programming despite I created and sold 3 games in a long time (a bit after the Middle Ages). I am a petroleum geologist working in Africa, so internet speed is not always optimum to say the least.

Powder Toy:
Good points so far: pretty powerful, a lot of elements available, rather good physics (although I noted some issues with liquid especially with U tubes)
Bad points: graphically not at the top, very poor tutorials, not available for all (I have a feeling of a tool afraid to be too attractive to the 'mass')

Why I am still interested: the plus seems, so far, stronger than the minus and it might improve in the future. I am very interested in simulating geological process.

I already have suggestions for elements but I want to structure it correctly before submitting.

I released in 1983 a game called Rigel, produced by Ere Informatique in France. It was an scifi exploration/strategy/adventure game, exploring a planet, defeating vicious pirates who were trying to exploit the inhabitants. I release in 1983 another game called Argolath, a hack & slash in a maze, RPG style. Both were on ZX81. Finally I released in 1986 Ethnos on Amstrad CPC and Thomson computer. The game was a precursor of Civilization style game except there was a possibility to use the gods for help and the aim was not to defeat the other civilization but to merge.

I already start to understand a couple of trick, wifi, aray etc... Quite exciting. But the GUI, gosh, something needs to be done... Apart from that, this simulator is incredibly powerful. In the oil and gas industry, we use FE simulator to simulate the flowing of oil/gas in a porous reservoir. I will try to achieve something like that when I have time, simulate gas/water injection, coning etc... It could be interesting if a multiphase is possible. Presently, I found that sand is not presenting any permeability or porosity, that reduce the possibilities or make it tougher. Surface tension and other factors needs also to be simulated. This is a bit difficult.
Another domain interesting me is the simulation of folding. I did some very interesting works with OE-Cake already concerning diapirism of salt (salt is lighter than the rest and tends to move up, piercing the overlaying rocks in kind of giant mushrooms).

I want also to simulate the natural atomic reactor of Oko in Gabon.

Anyway, I don't want to make you bored with my geological diversion.