One time, we were drawing a state diagram of how the core loop in our application should behave. So, you know, first you have the preparation state, then when that succeeds, you go to the getting-things-ready state, then into the actual doing-things state, then the result-reporting state and so on. So, there was exactly one happy path.
Then we figured, we should also diagram all the error scenarios. If an error occurs in the preparation state, we should transition to the result-reporting state. But if an error occurs in the getting-things-ready state, we'll need to go to an intermediate cleanup state before we go to the result-reporting state, and so on.
As we added more and more error paths, the arrows had to curve more and more, until the whole diagram eventually looked like an onion. That's when I knew, we were doing real software engineering. 🙃