Most designers today create static mockups to communicate app ideas. But increasingly apps are anything but static, this is why I use Origami a tool for interaction design by the Facebook Design Team. A tool built upon a development language called Quartz Composer that I have 10 years experience developing with.
Origami is a tool for designing modern user interfaces. Allowing quick creation of prototypes that run on your iPhone or iPad, ideal for quick iterations and the added bonus of exporting code snippets for your engineers to use.
Inaddition Origami can prototype for desktop websites and apps with features like text input, custom cursors, FaceTime camera, OS X drag and drop, and a resizable web browser frame for prototyping responsive designs.
Facebook created Origami to help them design and build many of their products, including Instagram, Paper, Messenger, Slingshot, Rooms, and Groups.