From the campaign:
The deck is technically a oneway, alternated double-backer. “In English, please!” The face and back of each card are identical, that’s a double back. But the pictures are not mirror images across the center lines because one bird has wings up and the other wings down. That’s called a oneway deck. Then, the front and back side images are transposed. This alteration creates a thaumatrope when the card is spun on it's top and bottom corners and viewers are given the beautiful illusion of the hummingbirds flying!
Hate to say it but I kinda like this deck. Hummingbirds are nice. The shape at least
looks cool. But I can't do all that fancy spinning cards crap, I can grind out a dozen or so flourishes and, at least in my mind, it seems most of them depend quite a bit on having a rectangular deck. Am I willing to buy a deck that looks kinda neat, in the hopes that someday my cardistry becomes good enough to actually make use of this deck, so I can perform amazing visual effects for the audience I don't have and never will?
Probably not. On the other hand, I like curious things so who knows.
Also, the art reminds me a lot of this beer can art:
