Player 1: Stay behind the glass panel on your right (so you’re out of sight with the turret) and get a portal on the wall by the light bridge down below and then fire a low shot at the wall in front of you. This will create a protective barrier for player 2.
Player 2 : Now’s your chance to get a portal on the wall ahead and then up on the alcove just above you and to your left.
Player 1 : As soon as you notice player 2 passing through the portal, raise the height of your protective barrier, so the turret can’t kill your partner.
Player 2: Get a portal on the ceiling directly above the Arial Faith Plate and then get another one on the slanted wall panel to the right of the turret. Stand on the Faith Plate and watch as you knock it clean off its perch!
Player 1 : Follow in player 2’s footsteps and get yourself up to the alcove with the Faith Plate on it. Stand on it and you too will be whisked across the chasm and onto the second part of this chamber.
Player 1: Upon entering the second part of the test chamber you’ll notice the multiple turrets guarding the area to your immediate right. Your first task is to get a portal on the left-hand pillar with the turret on it and then a second portal about two-thirds of the way down the vertical concrete pillar directly ahead of you. This’ll create a barrier high enough to protect both of you.
Player 2: Wait until player 1 has stood on the large red button on the ground and when they do, look up towards the middle of the ceiling where a concrete wall panel will drop down. Shoot this and then shoot the panel behind you. This’ll allow you to drop into the middle of the room, directly behind the first two turrets. You’ll now want to shoot a portal at the wall panel up and to your left (just above the left-hand turret in fact). Make sure player 1 is ready and then turn and hit the red button.
Player 1: Stand back once player 2 has hit the button as you’ll want to catch the Companion Cube before it bounces off the wall and into the destructive water nearby. Once you’ve got it in your steely grip, set it down on top of the button, and then wait for player 2 to shoot a portal on both your side and on the wall panel above them (or you can even do that bit yourself if you prefer) and then step through the portal to join your friend on the other side.
Player 2: Once your colleague has joined you, you need to set a portal back up on the left-hand hanging wall panel (above the turret) and then another on the patchy pillar further to the left (directly facing said turrets). Now either you or player 1 needs to push the button to release the balls and Cubes, knocking over both sets of turrets!
Both Players: Now it’s just a simple case of making a run straight for the exit and the final test chamber on this course!