Top down and bottom up have little to do with using long functions and not separating code in multiple files. In top down you start with a high-level overview o

Top down and bottom up have little to do with using long functions and not separating code in multiple files. In top down you start with a high-level overview of the system and gradually break it down into smaller and more detailed components as it provides a clear and structured view of the system. In bottom up you start with the individual components or modules and gradually combine them to create larger subsystems or the complete system. Each approach is suitable for a type of problem. I personally prefer to start off a POC as bottom up then once the general shape of the system emerges a rewrite top bottom is a good idea. I've seen lots of systems that started as top bottom and the architecture was atrocious because it's final shape wasn't know at the beginning, it was great on paper though. There's no silver bullet, there are multiple ways to solve problems and they all have their pros and cons. The takeaway is part is that applying methodology dogmatically is not a good idea.