Fun Mental Exercises

On my flight back from Minneapolis to Columbus, I noticed that the girl sitting next to me was doing this interesting number puzzle game. Intrigued, I asked her what the puzzle was, and she went on to explain the basics of Sudoku. Without getting into too much of the details, it's basically searching for a particular arrangement of numbers from 1 to 9 without overlapping each other. She gave me one of her pages in her Sudoku book for me to fiddle around with, and I got pretty hooked solving 4 of them on the flight back. And today, I finally found a web version of it! So if you like number puzzles, definitely check it out! It might seem simple at first, but I'm sure the hard ones will make you cry :P