The cat picks a number between 1 and 100 and you have to guess it. For each guess, it will tell you whether its number is higher or lower than your guess. How many turns does it take you? This is from the book Coder Academy.
This project is from Coder Academy, by Sean McManus. Find out more and get a free sample chapter here: http://www.sean.co.uk/books/coder/index.shtm