Diffusion, moving

A structured medium of chambers, each with its own internal architecture of bars, mottle or posts, flooded from two point sources carrying two substances. A weighted search spends a fixed budget: one step inside a chamber, seven to squeeze through a gate in a chamber wall, and a wall without a gate cannot be crossed at all. Concentration is quantised into eight levels and drawn only as counted marks per lattice cell and steps up a Flexoki hue ramp. Nothing fades and nothing blends. Where the two fronts overlap, a cell stops reporting concentration and starts reporting the mixture, nine squares split between the two hues by count.

The still is called arrested, which gives the game away: a diffusion is a process and the plate is the moment it stopped. Here the budget breathes, so the fronts run out through the gates and draw back, and the seam where the two substances meet travels with them. The frame at rest is the full budget, which is the published plate.

The medium itself does not move. Chambers, grain and obstacles are drawn once, because a medium that drifted would make the spread unreadable: what the piece is about is which way the resistance let it go.