Play with sandpiles, mathematical constructs that have simple rules and odd properties.
Use a brush to pour sand on, or go by singular grains. Flatten to any height with the brush or using the menu. Swap out colors with the built-in palette.

Options:
❎: to brush
🅾️: to palette
arrows: select options
Brush:
❎: paint
🅾️: back
arrows: move brush
Palette:
❎: switch theme
🅾️: to options
arrows: select options

Feedback appreciated!
inspired by Numberphile

sand sandpiles zen art