Cards "in play"

[itjunkie]

When is a card considered to be "in play?"

if i have cards stacked on Here is Good Rock , are those cards considered to be in play?If that is the case, can I discard dwarven cards stacked on Here is good rock or Preparations to use Grimir, Dwarven Emissary's 11R10 Game text?

Also, if the card stacked on the condition is considered to be "in play", then does that mean that I can't stack a copy of here is good rock on here is good rock? since there can't be 2 unique cards in play at the same time?

[Thranduil]

Stacked cards are not in play and cannot be spotted, unless a card is specifically looking for them (eg. Axe of Erebor, Battle Tested).

Thran