Each player selects a card (or combo of cards) to play each round. The player with the higher number wins the round and is able to apply that damage against their opponentÂ’s defense that round. This is depicted as an animated sequence...

There are three kinds of combos that can be unlocked through game-play. They are: Attack combo, Defense combo, and Action combo. These combos allow the user to combine the power levels of multiple cards in a single play. Once unlocked, a card with a 5 star Attack, for example, can be combined with other cards with 5 stars.

Via Siliconera