It's a neural network rather than a bunch of hard-coded rules. That turns out to make a big difference. Actually, there's this interesting snippet from the re

It's a neural network rather than a bunch of hard-coded rules. That turns out to make a big difference. Actually, there's this interesting snippet from the release page: > These techniques have been applied to hundreds of billions of training positions, all of which have been consistently rescored using a strong Leela net. So Stockfish's neural network evaluator is actually trained using Leela Zero.