A handful of grains and a little water, on a grid with edges
and nothing to win. Sand falls and piles; water falls, spreads and sits
under the sand; stone stays where you put it. When it has all settled, the
page is a picture of a pile, which is the entire point.
The rest of the family is that way.
How it works
Keyboard: arrows move the cursor, Shift moves it
further, Space pours one brushful, and 1–4 choose sand, water, stone or the
eraser. The simulation only runs while Pause says Pause; with reduced
motion asked for, it starts paused instead of moving on its own.