Go into the museum and from the information booth, go right and up the stairs. Now, turn
to the left and you will see a room next to the game rooms called the X-Room. Go into this
room and hold L1+L2+R1+R2+Up simultaneously. With these held, press triangle. You will
hear a sound and the room will flash white for a second.
To the right of the dark room
will be a woman with green clothes. Stand in front of her and press X. She wlil then
disappear and you will be left with the pedestal in the middle of the room and the words
"Assault Plus" flashing above it. Access the pedestal and the arcade game will
be the new Assault Plus game!