I’m not sure I’ve ever tested out an easier prototyping engine than Fluid. Seriously, you have to give their editor a test drive, it’s incredibly simple, intuitive and has a robust pallet of drag and drop user interface components that snap to the grid and size intelligently.
Fluid has custom player apps for Android, iPhone and iPad. They allow you to build connected multi-screen prototypes, export the screenflows, add gestures and transitions with swipe, tap, double tap, slide, fade and flip actions. Aside the over 2,000 ready-made iOS, Android, Windows 8 and wireframe UI widgets – you can also upload your own images.
Depending on which plan you select, you can have multiple active projects, forum and/or email support, active projects and custom loading screens. Every plan comes with unlimited inactive projects, unlimited pages per project, version history, the ability to test on a device, and sharing for team collaboration. Fluid also offers an enterprise platform available to agencies and corporations.