Very cool idea, I love poker so this is really great! However, 15s not long enough! You need to understand the cards in the middle, figure out which one needs to lose/who's bet what, what they have in their hand vs the other player, and find a card that's not already in play to scramble things all within that short time.
For developing further, you could look at extending the timer/allowing people to choose how long they have, having clearer key information indictors / colouring, and a tutorial / tips area or feature would be great!