Before Replay Builder, a common pattern would be to use Claude or ChatGPT to explore an idea, and work with the LLM to build a robust prompt to then copy/paste into your tool of choice.
Well, Builder was trained for this. Think of it as your thought partner/personal product guru that will take your loosely structured app idea, and ask you a series of clarifying questions. By the end of it, Builder will reflect back what it believes will be a bullet-proof prompt.
From there, you tell Builder to start building, and it will construct a robust plan of attack right before your eyes. It'll even write its own tests for each feature of your app to make sure the code it generates actually works.
Happy building!