Hexagonal Abelian Sandpile, 6 grains per cell maximum

Adding grains of sand, one at a time, on a hexagonal grid. When a pile reaches 7 grains of sand, six are given to its neighbors. A black cell indicates no sand, increasing brightness indicates 1-5 grains of sand, and yellow indicates 6 grains: on the verge of spilling onto its neighbors. The pattern that emerges is rule-dependent, stable, and scale-independent. Rule-dependent: the number of grains allowed per cell changes the image you get. If you spill at 6 (leaving none in the source cell) or 8 (leavin