LOL, i saw that the other day...took me like 10 seconds to figure it out, then i wrote the program in my programming class and bedazzled everyone.

It works if you know that if you do the reverse-subtract method they talk about, for ever number, it could only land on 10 possible other numbers, of 100.

For example, look at 81 (which is one of those 10 numbers). That symbol should be the one thats the answer every time.

Then after the flash is done, it randomizes the symbols again.