the idea is fine but it would be better that instead of a timer the game is in turns and the opponent does more than just leave their cards on the table ... if you develop it better you could make an excellent card game per turn

This is a neat idea, I found that if I just kill the minion that negates damage on the boss, then I can just mindlessly drag all of my cards to the boss and win, so I feel like there needs to be a cost to using cards or some reason to read the cards and use them or not.