The amazing, autotuning sandpile, https://nautil.us/issue/23/dominoes/the-amazing-autotuning-sandpile
Jordan Ellenberg on abelian sandpile models (https://en.wikipedia.org/wiki/Abelian_sandpile_model), with pretty pictures of the fractal patterns they generate, from 2015.
These patterns are still a topic of active research; see e.g. "The Apollonian structure of integer superharmonic matrices", Ann. Math. 2017, https://annals.math.princeton.edu/2017/186-1/p01, and "Harmonic dynamics of the abelian sandpile", PNAS 2019, https://doi.org/10.1073/pnas.1812015116
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