Particle Simulations/Games
In particle simulation games, particle materials like virtual solids, liquids, and gasses are painted onto the screen for observing how they interact. While the behavior of any single element is simple, the interactions between the elements and across the space is where the interesting complexity of the simulation unfolds.
Powder Game
After selecting a particle material or phenomenon, it can be "painted" onto the screen.
Sandspiel
Created by max bittker.
Making a falling sand simulator
A programming tutorial (using p5.js).
Rain on a window pane
In the rainyday.js simulation by Marek Brodziak (2013), small raindrops combine to form larger water drops, which eventually float gracefully down the window’s glass. See also the author's article.