Effect:
Let the audience draw a card, mark it or sign it, and insert it into the pile. The magician shuffles the cards, puts them in the card box and covers them. Take out a balloon, put it on the seal of the card box, puncture it with a needle, and the card box falls to the ground, leaving a card in the magician's hand, which is the audience's card!
The magic secret:
Knock the audience's cards down with a fake cut or pass. When you cover the card box, pay attention to the depression on the box cover. See? Put the first card here, face yourself, take the balloon out of the place where it is placed on the lid of the card box, and take out the first card at the moment of breaking the balloon (be sure to synchronize). Of course, cards are the audience's cards!