Invader (Prentice-Hall)

From the book "Brain Games for Kids & Adults Using the Commodore 64". If you think that the Swedish Navy is inept at catching those small submarines that creep into its territorial waters adn seem to escape at will, then here is your chance to see if you could do any better! this game sets up a 9x9 array of points. The points are displayed on the screen in 9 rows and 9 columns, each being numbered. There is one invading sub in each row. You must locate all the subs in just 40 moves.