Reach the puzzle for Extractor 5 at the start of Chapter 5 of the Mines. In order to solve the puzzle in one attempt, you cannot release the lever once you grab hold. Do not touch the lever until doing the following preparations. Drop a light seed down each of the two left-hand tubes. Then, drop a dark seed down each of the two right-hand tubes. Next, drop a light seed next to the grate below the lever and water it. You can now grab the lever and switch the lights from side to side until the last fluro reaches the green switch at the bottom and opens the gates.