Ink on wet paper where the paper does the work: capillary spread that feathers on the wet side and stays crisp on the dry, strokes that end darker than they begin, and the dry-brush streaks of a nearly empty brush.
Drawn with: a WebGL2 shader.
Reacts to and looks like: gpu, webgl2 and audio-reactive.
Family: Visualiser.
Runs in your browser. The preview above is the same program the renderer uses.