To be unfunny:

The whole idea of a balls hitting each other universe went out the window when we hit the quantum era. We have had to adapt to a reality where matter is somehow a statistical phenomena, and the details are always hidden from us in one way or another. Entanglement is another confusing thing, and its super common - not just some rare phenomena in a lab, it's more of a fact of particle interaction

So our brains are somehow statisical-chemical-electric sugar powered supercomputers that have entangled state. And the brain actually stretches across the body, with various chemistry being produced throughout

In short, nobody has any idea how brains really work, it's way more elaborate than current AI. It's also likely impossible to fully simulate a brain - it would have to BE a brain

There's a separate question about the nature of randomness in the universe, but all we can know is that follows a normal distribution over time. It seems truly random from our point of view. Of course, who's to say if God likes to fudge the numbers a little