"""Galton board: balls dropping through a pyramid of pegs onto a 3D mound.
The flat board sorts balls left or right at every row and stacks a bell in a
row of bins. This one sorts them in two directions at once: each peg sends a
ball half a step along x and half a step along y, so after six layers it
lands in a 7 by 7 grid and the stacks grow into a two-dimensional bell, a
mound you can walk round. Each axis is its own run of six coin flips, so the
mound is the product of two binomials, and the normal toggle stands each
axis's marginal bell on the far wall behind it.
Every ball is decided up front from a fixed seed: which way it goes at each
peg, when it launches, where it lands. The still, the layers and the loop all
read that one record, so the heights in base.png are the heights the loop
ends on.
The loop is a oneshot: stacks only grow. Balls keep launching until nearly
The full Manim source and the rendered video come with a plan.
