Thanks for the feedback!
I tried to reduce the amount of handholding with each part, but maybe it is a bit too much in part 3 and 4.
You can read the complete code on
github. Each chapter has its own tag in the history. I was thinking of writing an introduction to the tutorial where that fact is mentioned, but I'll also consider adding a direct link to the code for each chapter at the end of each one.
If I can gather enough motivation I'll finish the remaining parts in the near future.