After Burner (Sega)

On the title screen, type "CHECKDISK" and it will check the program
disk for errors.  During play, hold down "ZXCUIO" and the screen will
flicker.  Make sure you press them in the given order.  Now use the
following keys:

 F5   To add extra lives.
 F6   Subtract from current stage number.
 F7   Add to current stage number.
 F8   Go to the selected stage.
 F9   Go back one stage.
 F10  Advance one stage.

The up and right cursor keys increase something by one and the down
and left decrease something by one.