Contour maps, made by two waves crossing.
The idea is unusual and worth following. Pick a geometric figure: concentric circles, a polygon, a diamond, a straight ramp. It never gets drawn. Instead the figure is used to decide *when* each pixel gets its turn. Pixels near the centre of a circle figure run slightly ahead, pixels further out lag behind, and the result is a wave that travels outward through that shape.
Two of those waves run at once, each with its own figure and its own speed, and their values are added together. The sum is then folded at its midpoint, so values above the middle come back down again. That fold is the whole reason the picture has crisp contour lines rather than a soft blur: where the two waves add up to exactly the midpoint, the fold produces an abrupt edge, and those edges trace out where the two figures interfere with each other.
loopAOffset and loopBOffset pick the two figures.