Off-topic but funny: The Flash Mind Reader

I know this is old, but I've just figured out the trick -after a great number of tries
Needless to say, don't spoil it immediately, haha. Have fun with your friends and relatives first:

All your mind are belong to the crystal ball
It works to a formula.

I read about this ages ago, but can't remeber the details.
Every number you can possibly come up with is the same symbol as what ever is going to be in the crystal ball. The symbol changes each time you play the game.

I'm not exactly sure how to write out the formula though... function of x = d1d2 - (d1+d2)?? d meaning digit.

edit again: redundancy check
it works off of multiples of 3

81, 63, 45, 27, 9 will always show the picture it's about multiples of 3 i could write a mathematical formula for how it works but i'm not going to it's late and i'm not a math person just a patern recognizer something about the way i think i'm also good at voice patterns writting paterns blah blah blah.

yet i cant spell eh

but since i'm bored and i can explain the zero easily it's because if somebody was like i'm going to be cleaver and try to fool the magic ball by not picking a 2 digit number (so if you take a one digit number and minus it from itself you get zero)

and one more time since i'm bored if you wanted to write this up for yourself and make it more fancy you could have all the symbols change as long as the multiples of 3 are the same symbol and then all the rest are just randoms. this site has fixed symbols for every number that isn't a multiple of 3(note again i'm not a math person so if i'm not using the right term then eh what ever)