To defeat the second Gloktogi (the octopus-like robot) you meet, before you meet the final two, jump upon the crates until you land upon the container wall. In the distance in front of you, you will see a glass door. Shoot it and walk slowly towards it. Do not fall off the container. If you do, this you will draw out the Gloktogi. Let it web you a few times to draw it directly in front of you, then step back until you land on the crates. You will be able to look over the rim and fire at will. The monster cannot reach you. Use the Zapfly. This will save ammunition, but it will take a while.
