Challenges

1. Improve the function ask_number() so that the function can be called with a step value. Make the default value of step 1.

2. Modify the Guess My Number chapter project from Chapter 3 by reusing the function ask_number().

3. Modify the new version of Guess My Number you created in the last challenge so that the program's code is in a function called main(). Don't forget to call main() so that you can play the game.

4. Write a new computer_move() function for the Tic-Tac-Toe game to plug the hole in the computer's strategy. See if you can create an opponent that is unbeatable!