Bloom

drop ink twice. the wet half decides.

drag ink across a damp edge and watch one stroke do two things

Watercolour has one rule under everything: pigment goes where the water goes, and stays where the water leaves. Drag the brush across the damp edge and the same stroke does two different things — on wet paper the pigment keeps travelling and feathers out, on dry paper the water soaks straight in and the edge locks where you stopped. Nothing about the brush changed. The paper did. This is the shallow-water and pigment-deposition part of Curtis et al. (SIGGRAPH 1997), cut down to what runs in a phone frame.

Concepts: fluid-flow, color.

An interactive you play with one thumb, on Wundr.