Only complaint is the store...buying boat loads of oak packs takes so long. I would recommend having a value at the bottom of each pack saying how many you'd like to purchase or a X number of cards in a new version of the oak pack like oak bundle and just removes the selection of which card you want/upgrade (example 250 coins for 3 cards where you don't get to select but you save 50 coins due to loss of selecting 1 out of 3 cards)
 "War of Omens"){kind=icon}
 "Shield Defense"){kind=icon}