Walk up to a door you wish to pass and turn around so your back is
        to the door.  Hold down your fire button and tap the joystick in the
        opposite direction to the door.  Then push the joystick towards the
        door and release the fire button. (THIS IS TRICKY)

        The level codes are:

                          1      2      3      4      5      6      7
            EASY:      "BACK" "LOUP" "CINE" "GOOD" "SPIZ" "BIOS" "HALL"
            NORMAL:    "PLAY" "TOIT" "ZAPP" "LYNX" "SCSI" "GARY" "PONT"
            DIFFICULT: "CLOP" "CARA" "CALE" "FONT" "HASH" "FIBO" "TIPS"