Player 1: As soon as you land, turn left and then get a portal on the thin wall panel where the vertical light bridge is hitting, then look for an identical thin wall panel to your right. Set your second portal here, extending the light bridge and blocking off the turrets tucked away on the right side.
Player 2: Follow player 1 down the room, but halfway down turn to your left, look up and fire off a portal on the tile the excursion funnel is flowing into. Now both of you need to turn the left corner and you'll want your exit portal on the wall panel here.
Player 1: Both of you should jump into the funnel and you'll be carried over a chasm with spike panels all around and a conveyor belt of infinite turrets directly below you. So as you're passing over the metal spikes, look down towards the conveyor belt below and directly under the left-hand metal girder is a thin rectangular wall panel. Get a light-bridge here so it'll protect both of you from the turrets in just a moment.
Player 1: There's more tomfoolery with the light bridges, so get a portal on the wall of the light bridge and then look up and to your left where the three turrets are located. There's a conveniently placed wall panel just in view, so get the light bridge barrier up here to protect both of you.
Player 1: As you ascend the funnel, keep your eyes open for viable wall panels to shoot your portal on, there's an abundance of turrets tucked away in little crevices on the way up, shooting the portals in the walls will create protective light bridge barriers.
Player 2: Once you reach the top, step off onto the platform (near the other vertical excursion funnel) and look for yellow wall tiles just over to your right in the distance. There's a wall panel big enough to shoot, so place your excursion funnel portal here. Now jump into the nearby vertical funnel (along with your metallic buddy) and you'll be carried along to a platform, once you've dropped down safely, aim up and get your funnel portal on the wall up here. Head up the stairs with player 1, jump in the funnel and then jump out at the end onto the other platform.
Player 1: First thing to do here is to go to straight ahead and then look through the broken panels to the vertical excursion funnel to your left. Set a portal here and then on the wall panel located a bit to your left.
Player 2: Your task is to take control of the light bridge, so peek through the broken panels and look down to the lower ground for the light bridge (zooming in will probably help). Once you've got your first portal on target, run around the corner and look for the turrets tucked away to the left (just past the ledge). Block them off with a light bridge on the wall panel here.
Both Players: The two of you need to jump into the excursion funnel and ride it all the way to the wall at the end. Player 2 should place a light bridge on the wall near where the turrets are coming from (creating a barrier that'll knock them off the conveyor belt). Player 1 now needs to look for a small square-ish room with a broken roof located down below you. If you zoom in, there's a wall panel you can place a portal on, so do this. You'll both drop down and as you're being transported along, get player 2 to look for a thin rectangular panel just behind a metal girder, they can place a light bridge here, making it impossible for the stream of turrets to hit you. Once you reach the end, hop off towards the office and hang a right when you enter, the optical disc you need is on a table at the back. Now simply pop it in as per usual to finish course 4!
Welcome back to Aperture Science, a world where your Companion Cube isn’t you’re only company. Take control of Chell once again in Valve’s sequel which takes you on an humorous and puzzling adventure and in our detail-packed guide we’ll show you:
How to solve every test chamber first time.
Conquer every co-op chamber with a friend.
Loads of High Definition screenshots and videos showing you the solutions to every single chamber.
High Definition strategy videos for every achievement in the game.
Uncover all of the hidden secrets and Easter eggs.