Starting from the Level 5 you can buy Powerup bonuses to boost your results:
This bonus freezes game time for a while each time you collect a bonus card.
Upgradable. At the beginning, it will freeze timer for 1 sec. Every upgrade will increase this time.
Available from the Level 5.
This bonus gives you the ability to expose any card.
Note, that one Jester Bonus is used when you start to play, not when you put it to the deck.
So, actually, you can use it 3 times per game(1 time in every round).
Available from the Level 9.
This bonus gives you +10 000 points each time you collect a bonus card.
Upgradable. At the beginning, you will have 2 power cards in the deck. Every upgrade this amount will be increased.
Available from the Level 11.