~ BIG GUN ~

Head towards the door in front of you and grab the Combat Suit on the crates to the left.

Go through the door to see a large diamond-shaped object shooting a red laser beam into the sky. There's a locked door across from you with a red light and another locked door to your left.

Approach the door on the left. Hop on the platform to its left and ride it up.

A boss, resembling a giant robotic fly, will appear. Use your BFG and Rocket Launcher to defeat it.

After the boss dies, your secondary objective updates to locking the laser in place. Head through the now open door with the red light.

Go right and down the stairs. You'll see a laser beam to your left.

Go through the doorway on the right to a platform. Ride it up and continue, eliminating Guards.

You will enter a room with a button on the left. Do NOT press it yet. Continue along and kill the remaining enemies to reach the other side of the laser beam you saw earlier.

Now, go back to the button you skipped. Pressing this button will lock the laser beam from the beginning of the level.

You will have approximately fifteen seconds to escape the area or you will die.

Face the button, and after pressing it, run down the corridor to its left.

Head straight and slightly left to drop down.

Go right, then up the incline on the left.

Go right again and through the door on the left.

Run through the door on the right and quickly proceed through the corridor.

Enter the ship on the right to destroy the Big Gun and advance to the next area.