> They figured out a way to show you exactly what you're interested in, without you giving them any specific input They optimized their primary user interactio

> They figured out a way to show you exactly what you're interested in, without you giving them any specific input They optimized their primary user interaction to provide specific input! By distilling user choice down to {watch time} or {swipe}, and preferentially promoting short pieces of content that generate more swipes, they get unambiguous and frequent input. Which isn't to lessen their achievement, but is to highlight that they engineered their entire experience to provide their algorithms more and cleaner feedback.