yep, I already did the change : https://github.com/jDramaix/gss.gwt/pull/4

Sprite will not be a mixin because if it's the case, the developper will need to import a css file where the mixin is defined. so sprite will be GssFunction but as you said, it will (re)use what is done for the ```value()```  function

I'm currently working on the value function