Marvel vs Pop: What are the differences?
Developers describe Marvel as "Prototyping for everyone". A super simple tool that turns any image (including PSDs) or sketch into interactive prototypes for any device Powered by Dropbox.. On the other hand, Pop is detailed as "The extensible iOS and OS X animation library behind Facebook's Paper". Pop is an extensible animation engine for iOS and OS X. In addition to basic static animations, it supports spring and decay dynamic animations, making it useful for building realistic, physics-based interactions. The API allows quick integration with existing Objective-C codebases and enables the animation of any property on any object. It's a mature and well-tested framework that drives all the animations and transitions in Paper.
Marvel can be classified as a tool in the "Interactive Mockups" category, while Pop is grouped under "Mobile Prototyping & Interaction Design Tools".
Pop is an open source tool with 19.7K GitHub stars and 2.9K GitHub forks. Here's a link to Pop's open source repository on GitHub.