You can try that link or play with it here. I will give the answer for the first 4 replies.

1) Think of a 3 or 4 digit number and write it down.

2) Scramble the digits of that number.

3) Calculate the absolute value of the difference between the two numbers from steps #1 and #2.

4) Circle one of the digits in the difference. Don't circle zero. Report the remaining digits.

5) I will respond with the value of the digit you circled.

John