All Weapons + 500 Ammo:
Enter the code 'A, LEFT, A, B, A, RIGHT, A, C, A' on the map screen.

All Items on Map:
Enter the code 'LEFT SHIFT, RIGHT SHIFT, RIGHT SHIFT, RIGHT, UP, B, B, LEFT, RIGHT SHIFT' on the map screen.

Reveal entire Map:
Enter the code 'LEFT SHIFT, RIGHT SHIFT, RIGHT SHIFT, A, LEFT, LEFT, UP, A, C' on the map screen.

Level select :
Enter the code 'LEFT SHIFT, UP, C, C, RIGHT SHIFT, DOWN, A, LEFT, LEFT' at the map screen.

Note: reboot to select any level.

Larger Screen :
Enter the code 'UP, RIGHT, LEFT SHIFT, UP, RIGHT, RIGHT, RIGHT SHIFT, A, LEFT' at the map.

Note: reboot to change the screen size.