Enable the "Secret rooms" option. Do any
one of the following to enter a room called Chow Palace, which
is filled with power-ups.
Inside the bunker, shoot all the blue lights on the left wall.
Shoot out all the back windows inside the bunker.
When riding inside the forklift, shoot all the yellow barrels.
When riding inside the jeep, shoot all the yellow boxes.
When you are in the building shoot the name plate off the second
door as it is opening.
When you are being bombarded by the two aliens on top of the hill,
shoot everything yellow.