Assault Suit Leynos

The hidden path is located about halfway down the section inside the enemy base, at the bottom of a shaft on the left side that has several small platforms and 3 floor lasers and looks like a dead end. Stand on the lowest platform, aim your gun diagonally at the lower left corner and keep firing. (You don't want to drop down to the floor because the lasers there will drain your suit's energy very quickly.) Eventually you will see a small explosion and a score of 1500 points will appear. Drop down and move to that corner, avoiding the floor lasers as much as possible, and you will fall into a secret shaft that will let you out just before the reactor boss at the end of the stage. You need to actually use the passageway to get the trophy. Merely blasting it open is not enough.

Note that you cannot obtain this trophy in conjunction with "Turret Buster I" because taking the hidden path will bypass some of the gun turrets.