I use Flinto to test interaction on my prototypes. The way the user can easily create transitions, action buttons and animations makes faster the design process of an app. Compare with other tools like Principle, Flinto for Mac allows to prototype complex behaviours through an intuitive UI of native Mac OSX elements. Best feature is the possibility to "reverse" the transition, the live preview and the Sketch plug in that export directly in layers.

- A UI familiar to any Sketch user - Mobile companion app - Easy import from Sketch