I always think of Conway's Game of Life in this regard. He (Conway) seems to not think that much of his invention, but to me it it THE understandable proof that nearly anything can emerge from simple rules. Even the Game of life itself [0]. It's the basis of Permutation city (Greg Egan) [1], from 1994 (!) That guy is so ahead of his time, him and Ted Chiang are my fav authors.

This stuff is like staring the universe into its soul.

[0] https://oimo.io/works/life/

[1] https://en.wikipedia.org/wiki/Permutation_City