Exercise 19. Add backpropagation scaffolding.

Now we get to the grittiest part of this operation. If you haven't already, I strongly recommend you watch the video below on how backpropagation works, or read the blog post. Getting a feel for what it's trying to do will be necessary before we can reduce it to code in our next few lessons.

If you're inclined to dig deeper into math behind backpropagation, please check out this playlist from 3Blue1Brown (aka Grant Sanderson) a mathematician and YouTuber of phenomal teaching ability. He can make the most abstract concepts feel comfortable.

Coding challenge

My solution

Here is all the code we've written up to this point.