In it he showed that by mining Flowtypes from props he was able to visually wire up components to APIs and other components. Every time he pulled an edge out from a node everything would be grayed out except the props of nodes that could handle that type. In this way applications could be visually snapped together out of components and APIs. I saw that types are really like the modular connectors that you have with the pipework under your sink. They tell you exactly what can connect to what without getting leaks. And it turns out that types and fast feedback are not mutually exclusive.