When you start, it is pitch black. Switch to navigation. Go out and to the right. It doesn't matter which tunnel you choose here because both go to the same place. Go through that tunnel to the APC and past it. Go through the tunnel to the narrow walkway. Don't fall off here because there are spikes and it will kill you. Instead, climb up to the ceiling and go through the hole. Go through that tunnel and to the hole at the other end. Drop down and claw through the door. Destroy the two generators and go back up the hole. There is a turret in the other tunnel so do not go down it. Go back to the narrow walkway and go to the side you haven't yet. Go through the tunnel to the big room. From there take the passage on your left. Go through the end and through the APC. Go out the door and to the right. Go out the door on the left, then the door on the right. Climb up the far side of the wall onto the cliff. Go through the tunnel, right then left. Cross across the computer then through the tunnel. Destroy the turret you have a lot of life just run ahead past the next turret, otherwise backtrack to the computer room. Jump down and turn around. Go through the tunnel until you are at the turret. It may get a few shots off on you so be careful. Destroy it and go up the stairs. If you just ran past, you're already here. Go through the entrance and the Predator will jump down. Kill him with the standard powered up tail whip and follow up to end the level