A spectator pulls out a few cards from a completely normal deck.

Among the cards he chooses one which he turns face up in the rest which is face down, so that everyone can follow the magic trick, and shuffles the small paquet.

The magician is really blindfolded and sees absolutely nothing, yet in a few seconds he knows the position of the card turned over and chosen by the spectator, more over at the end he guesses the card which he has never seen !

Very easy to do !
Totally impromptu !
Instant reset !
Possible with any number of cards !