This web site can read your mind!

[Perry]

http://www.milaadesign.com/wizardy.html

For best results, turn on sound. :-)

[Dingfod]

How does that work?

[godfry n. glad]

How does that work?

I tried it several times and it was about 50% correct.

[Adam]

I've tried it about 20 times and it's been unerringly correct for me, but I did note that there's a sporadic flaw that pops up. I saw it twice for numbers in the 70-79 range, but it's not there every time. Were all your misses in the same range godfry?

For numbers in the 70-79 range, the magic number is 63, but I noticed twice while clicking through that the symbol that should have been aligned with 63 was aligned with 64 instead. Could just be a graphical justification issue...both times, the animation moved on before i could verify.

[Ari]

I was expecting it to be a flash where sometime jumps out at you with a loud noise.

Solution:
I believe the equation is something like 10x+y - (x+y) = 9x. Which shows what's happening. The y doesn't matter and you lose an x to become a multiple of 9 instead of 10.

I think.

[bobeh]

If it doesn't work perfectly there is something wrong. It should be 100%.

Unless its programmed to intentionally make the odd mistake...ah so...clever that would be.