RE: [css-variables] are variables animatable?

± Yes, they're not animatable.  (Or rather, they fall into the generic bucket of
± "flip halfway through the timing function".)  I'll add an Animatable line to the
± spec.
± 
± ~TJ

Hum, can we specify they flip immediately by default? Because this is the behavior you want in order to keep variables no-op. 

Again: 
@keyframes { from { top: 0px; } to { top: 100px; } }
@keyframes { from { top: get(var-top); var-top: 0px; } to { var-top: 100px; } }