Most people use PyTorch without really knowing what's happening underneath. This series breaks the foundations down into the simplest possible explanations — one concept at a time, with code you can run and exactly what goes in and comes out. This is Part 1 of 5 . By the end you'll understand the five building blocks every neural network is made of: creating tensors, doing math on them, reshaping them, computing gradients, and bending them with activation functions. No assumed knowledge. Let's g