What is Proto.io?
Proto.io supports all the major mobile gestures and touch events like tap, tap-hold, swipe, pinch, and zoom. Interaction designers are not limited to a single ‘link’ transition anymore. Instead they can apply animated screen transitions like slide, fade, pop, flip, flow, and turn.
Proto.io is a tool in the Interactive Mockups category of a tech stack.
Why developers like Proto.io
Easy to get started with a good set of UI controls
Design on site, better than simply importing stuff
Try prototype on mobile device