You have am idea but typically you neither have a complete understanding nor a detailed view of the solution, and of course things tend to chanhe over time. Th

You have am idea but typically you neither have a complete understanding nor a detailed view of the solution, and of course things tend to chanhe over time. That's the key benefit of starting small and of iterating: it allows you to learn and to improve. You don't learn anything about your problem amd solution by writing a comprehensive design spec upfront.