# A Cool Number Guessing Trick! Or Brown’s Criterion in Processing

This is a fun number guessing trick, based on powers of 2 and the Fibonacci sequence, that even little kids can enjoy. You don’t have to know anything about the powers of 2 or Fibonacci to play this game, just basic addition up to 30. Yet, if you are more advanced, it is very interesting to see what lies underneath and even apply binary numbers to your guessing technique. Simon learned this trick from the Numberphile video on Brown’s Criterion.

Simon also made his own version of the game, based on prime numbers:

In this second part of the cool number guessing trick session, Simon shows his own version of the game, based on prime numbers. He discovered that it’s impossible to create this game for all numbers between 1 and 30 because some numbers (4 and 6) cannot be expressed as a sum of two different primes and was very upset about it. Yet he did manage to make the game and it works for all numbers except 4 and 6. To play the game, one player thinks of a number and the other player tries to guess it by asking whether the number is present on different sheets of paper. The answer is the sum of the numbers located in the top left corners of all the yes-sheets.

And please check out Part 3, where Simon actually programmed this game in Java (Processing):

Now it’s the computer guessing the number! The game is available on Simon’s GitHub to download at: https://github.com/simon-tiger/browns-criterion

Simon explained the rules in the GitHub README (because he “has a different writing style than Mom”, he said): https://github.com/simon-tiger/browns-criterion/blob/master/README.md