Behind My Back was originally published back in 2014. Since then, it has undergone quite a few changes making it easier, more effective and streamlined.
Here is how it looks now:
With the performer’s back turned, the participant selects a few cards and then discards one of them.
The performer correctly deduces the number of red and black cards, and high and low cards that remain.
The participant further discards more of the cards, and this time the performer correctly deduces the sum of the values of cards in the participant’s hand.
The performer than correctly names the cards and further stuns the audience by naming the one card that was discarded in the beginning.