Sand grains are added one at a time. When a cell exceeds threshold (4), it topples: sends one grain to each neighbor. Avalanche sizes follow a power law — the hallmark of self-organized criticality.
Statistics
Total grains added 0
Topplings (current) 0
Max avalanche 0
Avalanches logged 0
Self-organized criticality: the system drives itself to a critical state with no parameter tuning.
Avalanche size distribution P(s) ~ s-τ with τ ≈ 1.2 (2D BTW).