FEffects is a library that enables you to create visual transitions like motion-tweens for example.
The package actually offers tweens and Robert Penners' easings are used here.
In order to use FEffects, you need to install the library using haxelib, like that :
haxelib install feffects
Then you can use the library by adding
-lib feffectsto haxe commandline parameters.
FEffects is used especially to create visual transitions, but in fact, it's just a numerical value interpolation: The Tween class will compute the intermediate values according to the begin value, the end value the duration and the choosen easing function.