Portal Chapter 6 (Puzzle 14)
As you walk forwards you’ll immediately see the level exit but there’s no way to get to it until you activate the platform in front of it. To the right is a red button and closed door.
Walk to the left and stairs will appear as you get near to the gap. Walk up the stairs to the next room. In the corner on the left is a cube but there’s no way to get to it directly. Place a portal on the vertical tile on the roof just before the cube and then go back to the stairs. They will descend and form a gap once more. Place the second portal on the floor down below and drop down. You’ll be flung out towards the cube. Pick up the cube and drop down to the floor.
Drop the cube and place a portal on the roof above the receptacle. Pick up the cube again and drop it on the red button on the other side of the corridor. Go through the door and jump across the moving platforms to the other side.
Place the second portal on the wall opposite the light ball. This will hit the receptacle on the other side of the corridor and activate the platform near to the exit. Drop through the portal yourself and then hop onto the platform to the lift.