Face Down + Hidden Mana

So long as we know to manually adjust for those kinds of things ourselves, having most of the working done would be really handy.

Oh, also, if we're keeping this kind of system, then face down entities are more powerful than they were previously, hiding your mana as well as itself. I think that should be considered as an extra bonus when balancing.

Is it only playing a face down card that hides the mana, and not using another method (Holiday present or flipping an existing card)?