I don't need specifically to tween a class here...
I make banners and i often need to center elements into wrappers then uncenter them, so i use those "helper classes"
i use className mostly to to deal with responsive banners and adapt tweens values on portrait and landscape
i set different properties for one class in the css media queries part, i find it very usefull but it has some limitations with "helper classes"...
When it starts to be too difficult (portrait design is very different than lanscape design, easing should be different....), i have to manage 2 DOM, 2 timeline and use JS.
I'm just diggin' to find a easy way to build complicated design, i'm a bit lazy so i don't want to write too many code
Anyway thanks for your help and fast answers!