At the very bottom of the levels, there are pools of water. Once to the left of the balloon, move as far left as possible while at the bottom. Then, use the vine to swing up to the lowest level on the left. From there. go up one level. You will see a spider crawling back and forth. Push yourself into the wall on the left (using the "Pass through walls" trick) until you are in enough to be able to travel up when you jump. Continue going up until you are up above the game's levels. Once there, you can find invisible ladders, pools of water, platforms and other objects. All this is not visible until you find the spot(s) that can kill you; then you will be able see your location. Everything that is found in the game is all packed in one area. If you go up from here, you will end up at the bottom of the levels of the game.