Card Warp is a card illusion that was created by magician Roy Walton.
It starts out with the illusionist showing two cards.
then folds one card horizontally and the other one vertically.
slides the horizontal card into the vertical card so the horizontal card is inside of the vertical card.
The illusionist then flips the cards over so that the vertical card is inside of the horizontal card.
slides the vertical card back and forth, and the card seemingly changes from front to back while inside the horizontal card.