Pop
iOS and OS X animation library for physics-based interactions
...The API allows quick integration with existing Objective-C or Swift 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. By adding the project to your project and adding pop.embedded framework to the Embedded Binaries section on the General tab of your app's target, you can set up pop in seconds! The Pop interface is implemented as a category addition on NSObject. Any NSObject or subclass can be animated. There are four concrete animation types: spring, decay, basic and custom.