Whats the easiest way to learn how GPT works where its not a black box? I tried looking at the micro/mini GPTs but failed

Maybe its a tutorial or course....but I was excited to see more and more news online (mainly HN posts) where people would show these micro gpt projects...and someone in the posts asked how it compared to "minigpt" and "microgpt". So I looked them up and its made by the famous AI guy, Andrej Karpathy, and it also seems the entire point of these projects (I think there is a third one now?) was to help explain .....where they arent a black box. His explanations are still over my head though...and I couldnt find 1 solid youtube video going over any of them. I really want to learn how these LLMs work, step by step, or at least in high-level while referencing some micro/mini/tiny GPT. Any suggestions?