Grains added: 0
Last avalanche: 0
Max avalanche: 0
Total topplings: 0
About: The Bak-Tang-Wiesenfeld sandpile: cells topple when they reach 4 grains, distributing one grain to each neighbor. Boundary grains fall off. The system self-organizes to a critical state where avalanche sizes follow a power-law P(s) ~ s^(-1.2). No tuning is required — hence "self-organized" criticality. The histogram shows avalanche size distribution on a log-log scale.