De Bruijn's pentagrid

Five families of parallel lines, and every crossing grows into a rhomb: where two lines cross at 72° a thick one, at 36° a thin one, and together they make a Penrose tiling. Drag Slide δ: the horizontal family is offset by δ and one slanting family by −δ (the two drawn brighter), so the five offsets still add up to zero. The result is still a Penrose tiling, a different one, yet every rhomb that does not flip stays exactly where it was. Only at the moment a line sweeps over the crossing of two others do the three rhombs there flip at once: the hexagon they make keeps its outline, its inside is rearranged, and it holds as many thick and thin as before. Rhombs that have just flipped turn coral; often a whole row flips together. A faint coral tint marks the flips passed on the way straight from δ = 0 to where you are, and the corner counts them (each three-rhomb rearrangement once), counting back down as you return towards zero. The thick-to-thin ratio in the corner is counted on screen and wavers as you slide; counted over larger and larger regions it tends to φ.