These codes when entered at the menu allow you to view the hidden screens.

KP  Code
--  ----
16  Joystick fire button
17  joystick fire + right mouse button
18  type 'kei' fast
19  type 'cd' or 'h'
20  Joystick right + fire
21  joystick fire + s
22  joystick left + g
23  x + Joystick UP
25  help