Player 1: This Test Chamber is a relatively short one that introduces you to the new aspect of reversing the direction/flow of an excursion funnel. So to begin with, get a portal up on the square wall panel that’s located up and to your left of the entrance (where the funnel hits). Now move forwards a bit and get your second portal on the square wall tiles to your right. This in turn will create a path across the bottomless pit. Now stand on the Arial Faith Plate to propel yourself into the funnel. Once you reach the other side, pick up the Companion Cube hiding away in the corner.
Player 2: Once player 1 has picked up the Cube, stand on the large red switch found on the floor and you’ll both notice the colour of the funnel change to orange (this signifies that the flow of the funnel has been reversed). Player 1: Jump back inside the excursion funnel (with the a firm grip still on the Cube) and simply enjoy the ride as you make your way through the portals and towards the start of the excursion funnel itself.
Player 2: As soon as player 1 reaches the excursion funnel device, stand off the switch and look up and directly behind you - to your right - for a square wall panel. You want the exit portal to go here as this will direct player 1 towards the square wall panel.
Player 1: As you approach the barrier with the square hole (big enough only for the Cube), let go of the Companion Cube and simply step out of the funnel to the ground below. The Cube will automatically find its way to the square-switch, in turn opening up the exit for both of you.