Simulated annealing of neighbor pixel distances, using bitwise distance
d(x,y)= MSB(x XOR y), where MSB stands for Most Significant Bit.
The top-level, bit-7 cluster is imported from smaller 512x512 size simulation and expanded, then annealed just long enough to round off 8x8 square jaggies. Otherwise it would have taken years to form the cluster if I started from completely random configuration.
Anyway formation of lower level clusters took almost a week on my PC.