Duel is a unique two-player game mode in Concentration - the Memory Games. You can play it against a friend or against a computer opponent. The deck is split and the game is quite unlike traditional flip over.
Previously associative play was disabled when the user selected duel mode. With the new associative card sets it really makes sense to play a duel with custom associations enabled. So, it will be an option in the 5.0 release. We used the Pounce and Wag card sets to create the following demo screen shot.
Associative Duel Play • 5.0 Enables Associative Play in Duel Mode
Since the deck is split, Player 1 (upper half) plays with the "Pounce and Wag (Wag)" while Player 2 (lower half) with the "Pounce and Wag (Pounce)" card set. In this game mode the sets' respective card backs are used as well.
At the moment neither Concentration - the Memory Games 5.0 nor the Pounce and Wag card set pack is available. That's why this post is categorized under Feature Preview.