Backpropagation for people who are afraid of math

Backpropagation is one of the most important concepts in machine learning. There are many online resources that explain the intuition behind this algorithm (IMO the best of these is the backpropagation lecture in the Stanford cs231n video lectures. Another very good source, is this), but getting from the intuition to practice, can be (put gently) quite challenging. After spending more hours then i'd like to admit, trying to get all the sizes of my layers and weights to fit, constantly forgetting what's what, and what's connected where, I sat down and drew some diagrams that illustrates the entire process. Consider it a visual pseudocode.