Level Passwords:

Enter the following icons in the password
screen to be taken to the corresponding level: 

Level 4: Medal, Medal, Your Plane, Enemy Plane 
Level 8: Your Plane, Enemy Plane, Enemy Plane, 
         Medal
Level 12: Bullet, Enemy Plane, Your Plane, 
          Your Plane 
Level 16: Enemy Plane, Enemy Plane, Bullet, 
          Enemy Plane 
Level 20: Your Plane, Medal, Bullet, Your Plane 
Level 24: Bullet, Your Plane, Medal, Medal 
Level 28: Medal, Enemy Plane, Medal, Enemy Plane