Zener Cards (named after 'Perceptual Psychologist' Karl Zener) are a tool designed to test ESP.
Here's the set I made today.
As you can see, there are 5 cards with a different symbol on each. I label them as follows. From left to right:
1. Square
2. Star
3. Cross
4. River
5. Circle
The game as I would like to play it goes as follows.
1. I shuffle the cards, and deal them into a 'spread'. I photograph them reversed, and then face up. I then post the image of the reversed cards.
2. You look at the posted image and use the psychic powers at your disposal to intuit which card is which.
3. Post your intuitions.
4. After a sufficient period of time has passed to allow anyone who wishes to take part to do so, I will post the cards upright image, and collate, track and post results.
I hope that I've sufficiently explained how I think this should work, and that it is entertaining. 
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