If I choose not to play a card when the card's counter is zero, I am penalized because the card's counter resets. This should be changed in my opinion so that when a card's counter reaches zero, it remains at 0 unless there is some sort of status effect occurring.
There really should be an upper and lower level filter for the games because I don't like getting matched with a level 30 when I'm only 15. It'll help to balance team and duels, and people that are lower level won't dickride the upper level guys in team games.
When you enter a pack tournament, you should see your cards after you pay the entry fee, and then the game should ask you if you want to pay extra to keep the cards.
So I threw my plane at about a 90 degree angle to try and get the stalling achievement. My internet froze for a bit but now my plane is falling into infinity with the same velocity and altitude for 30 minutes now...
 "Rise of Mythos"){kind=icon}
 "Crazy Fairies"){kind=icon}
 "Zombies, Inc."){kind=icon}
 "Tyrant"){kind=icon}
 "Burrito Bison"){kind=icon}
 "Tasty Planet"){kind=icon}
 "Flight"){kind=icon}
 "TDP4 Team Battle"){kind=icon}
 "K.O.L.M."){kind=icon}
 "Gravitee Wars"){kind=icon}
 "Lucky Tower"){kind=icon}
 "Toss the Turtle"){kind=icon}
There is supposed to be... you can also create your own matches and limit the player levels that are allowed to join.