Large Language Models like GPT4 are now a key part of the technology landsacpe, but how do they really work? And can you code them up at home? In this tutorial we'll create a simple GPT and train it on a simplified dataset of children's jokes. We'll work against a new set of transformer encoder flow diagrams that intuitively match the code, and look at visualisations of GPT's internal representations in order to better understand transformers inside out!