There are 14 new chambers added to this version of Portal, and there are also six advanced chambers, which are enhanced versions of Test Chambers 13-18. For three more achievements, you'll have to complete these at least once. Another achievement requires you to earn at least one gold medal on any of these 20 maps, or one of the original Test Chambers 13-18. The three categories are time, steps, and portals used, and the easiest one to get a gold medal on is Test Chamber 14's portals used category since it's super easy to finish in only two portals. This was mentioned in the story page, but a video of it will be provided lower on the page.
The 20 chambers unlock in order; you need to beat Still Alive 1 to get to Still Alive 2, and so on. The Advanced Chambers, on the other hand, are unlocked from the start. As for finishing the chambers, you can read on what to do, or you can look up chambers in the playlist link here for easy access to all of them. I personally would imagine that watching what to do would be far more useful considering the type of game this is, but if reading works for you, then go for it.
Portal: Still Alive | Challenge Maps & Advanced Chambers
Still Alive 1
This first chamber is going to be very simple. Put a portal on the wall on your side of the large gap, then ride the moving platform to the other side and stand on the button there so you can shoot another portal past the door. Then ride it back so you can enter your first portal and get into the room. When you're inside, take note of the button on top of a column of black squares in the corner. Pressing this will open the door in front of the energy pellet receptacle, but you won't have to worry about getting up there right now. Place your blue portal next to the button for now, and then wait for the energy pellet to fizzle out before putting your orange portal on the wall it hits. Follow the pellet through the hole, stay away from the center of the button, and move your orange portal in front of the receptacle door. When the pellet comes back through your portals and heads towards the door, stand on the button so it can hit the receptacle and give you access to the elevator.
Still Alive 2
There's a small room on the side of the main one with a little window that you can shoot a portal through. Do so and enter this room, and realign the portal you came in from (if blue is in this room, realign blue) to be at the bottom of the pellet receptacle. Then drop through it back to the original room and put your portal in here under the energy pellet so that it reaches the receptacle.
The pellet opens a horizontal door in the original room with a white panel above it. You'll want to start an infinite drop so you can reshoot one of your portals on a small white floor halfway up the shaft. There's another window accessible up there that you can shoot a portal through, and passing through there will get you to the elevator.
Still Alive 3
At the start of this chamber is a button with a skull on it. Press it, and you'll see that the cube past the glass will disintegrate, opening the door to the room itself. To get into the room, put a portal near the doorway and another near you, then press the button and either run through the door or put another portal past it. There's a lift you can use to get to the real puzzle of the chamber.
In the next room is another skull cube and a little window, with an emancipation grid separating two rooms. Walk through the grid and stand on the other side of the window so you can shoot a blue portal into the cube room. Then shoot your orange one on the only white panel in this mostly black room so you can take the cube to the black room, and use it as a stool to get to the top of the blocks like you did with the companion cube in the story. Put the cube on a button at the top and step down into a corner so you can look through the door that the button opens. Shoot an orange portal in there and walk through to it with the white panel in the room. From here, you can shoot your blue portal into the white cube room. Walk back in there and reposition the blue portal to ground level, and push the skull button so the cube can drop down next to you. Take it to the button behind the door, which then opens the door to the elevator. Return to the cube room and walk through the emancipation grid to get to the end of the chamber.
Still Alive 4
The starting room has a cube dispenser and two small windows; it should be obvious by now that you'll need to shoot a portal through one of these windows, and in this case it'll be through the one with a button in the other room. Take the cube to the button and then return to the starting room. Then look up to the left of the window you used to get to the button to find a well-hidden alcove that you can get to. Portal yourself up there and stand on top of the switch. Since the cube is pressing down on the other switch, the door in front of you will open, and you'll be able to put a portal on the back wall past the door.
Walk onto this new button and drop onto the floor, then put a portal at ground level on a nearby wall. From here, you can shoot another portal back into the cube dispenser room, and inside there you should press the little button so another cube drops down. Take it back to the black room with the elevator and bring the cube up to the top where the button mentioned at the start of this paragraph is. Having the cube there will open the door to the elevator.
Still Alive 5
This chamber introduces something you've never seen before: electrical fields. You'll die if you're between the two circuitry panels when they're active, regardless of the distance between them, so make sure you're moving through them quickly. As for this first one, shoot a portal on a white wall near the button at the start of the chamber, then wait for the current to stop, grab the cube, and run off the other side. From here you'll be able to put your other portal down and get the cube to the button, opening the door to the next room.
The beef of this chamber takes place in this large, momentum-oriented room. There are two cubes sitting on a grid and, in order to get to them, you'll have to fling yourself into the cubes using the white walls on either side and a deep pit to the south of the cubes. Simply line up your portals (the ones on the walls having their tops slightly into the highest row of panels) and jump down after the electrical field is deactivated so you can get to it without dying. Do this for both cubes, and you'll be able to open the door to the elevator.
The next trick is actually getting to the elevator. You'll need to set up another momentum fling, but this time you'll have to fly across the grid long-ways. The setup is a bit different too. Use the white panel on the ceiling above the pit to put yourself in an infinite drop, and then reposition your exit portal onto the slanted panel as you fall when the grid turns off so you can fling yourself into space and towards the elevator.
Beat 5 advanced chambers
Still Alive 6
You'll be introduced to two new mechanics during this stage, which would be red and blue barriers of light. Touching a red light barrier will kill you, whereas blue ones merely serve as walls. You can, however, shoot portals through both of these. You'll have to do just that to get past a few red light barriers and proceed into the first real challenge. When you see a long red light barrier, look down for a white wall and floor just barely above the toxic chemicals at the bottom of this room. Portal yourself down there using another white wall near the start of this room, and then look up towards where you came from for another white wall that you'd otherwise not be able to see. Portal yourself up there, and then stand on the corner of this area so you can put another portal at the white panel placed behind the red barrier. Next to the white wall near you is a long drop down, which you'll have to use to do a momentum fling over the red barrier and towards the next room.
There's a white panel past another red barrier, and you can get through to the other side by putting a portal there and another one on the wall down below. Don't put it on the floor, or you'll be flung into a different red barrier that you can't see just yet. After a little more maneuvering around red barriers, you'll land on a button. Put a portal in front of you, and then another up above you across from a gap so that you can see the next door on the other side. Standing on the button opens the door, so you'll have to step off of it quickly, run through the portal next to you, and shoot another through the doorway before it closes. Past the doorway are some blue barriers that won't take much effort to get through.
In the next room, a blue light bridge (a horizontal barrier) with a turret on it will be above you, and there'll be a cube button for you to press. Take the cube and yourself up to the higher ledge using portals, and then immediately use your cube as a shield against the turret's bullets. Run backwards into a little alcove, and then to the right behind a short wall so you can use the white wall to the upper left to get to a button. This button opens the door behind the turret, but you first need to get rid of the turret. Walk with your cube in front of you straight up to the turret and knock it over, and then put the cube on the button so you can advance.
A big chunk of the chamber past this door can be completed using the same techniques you've been using up to this point, but I suggest bringing the cube with you. There's a turret that you have to put a portal right in front of, and the cube helps you stay alive as you try to deactivate it. After a momentum drop, you'll find yourself in a room with a bridge with three turrets on it. If you've managed to bring your cube this far, great; all you have to do is push the turrets over with the cube and you'll be good to go. If you didn't, then put a portal on the white wall above the other end of the bridge, and then run off the right side so you can use the white floor below for a momentum fling directly into or in front of the turrets. Get ready to grab one and fling them around if you don't land into them yourself.
Still Alive 7
This chamber consists of two different main rooms. There's the first room, which is mostly white and has a red barrier on the floor above two buttons, and there's the mostly black room next to it. Portal yourself to the other side of the barrier so you can then portal yourself into the black room. One cube will drop from the dispenser above, but you need two cubes. Move the cube out of the way and then head to the corner closest to the dispenser so you can set up an infinite drop using the ceiling and floor. You'll want to fall long enough to create enough momentum so that you can shoot yourself into the dispenser itself.
After you're in the dispenser, shoot a portal through a window and use it to make your way all the way through the upper area here. It shouldn't take too long (nor will it be too complicated) to get to a broken tube at the top of the area. Crawl inside and keep going until you land on the cubes stuck in the pipe, freeing them from the predicament they're in. Now that you've got way more cubes than you could ever need, take at least two of them to the white room and put them on the buttons underneath the red barrier so you can open the door to the elevator.
Still Alive 8
At the very start of the first room in this chamber is a turret facing your general direction. You'll have to peek out a little to get a good look at it and get a good idea of where it is. Put a portal next to it and walk through from the other so you can jump to the turret and knock it over. Then look up and away from the direction the turret was facing to find the laser of another turret pointing at a white wall protected mostly by glass. You'll actually want to portal yourself up to the white wall that the turret's looking at, and then jump up the black slanted angle next to it so you can place another portal in the area above the turret.
In this new area is a small button that dispenses spheres as opposed to cubes. It seems this didn't debut in Portal 2 either. The problem with the sphere is that it shows up on the black platform in front of the glass, so you'll have to put a portal on the white walls around it, quickly take it, and bring it back to the small button. When you have it, drop it slowly or while it's already on the ground to prevent it from rolling, and then put one portal on the slanted white panel and another almost directly below you on the floor. The sphere is going to be used to knock over the turret with the help of a momentum drop. You might want to save beforehand so you don't have to redo most of this process if things go wrong. After the sphere knocks the turret down, use the momentum fling yourself to get to the elevator.
Still Alive 9
You'll see an emancipation grid at the start of this chamber for no discernible reason. Walk past it and look at the energy pellet flying up and down, and then time yourself just right so that you run into the little black crevice past the energy pellet's path. The first order of business is taking this energy pellet and redirecting it into the turret that's out of sight using a portal aligned with its laser and the energy pellet. After it's down, move your portals somewhere else and run across to the room you started in so that the pellet wears itself out. Now that the turret's out of the way, you can portal yourself up there and into the second half of the chamber without any fear of being killed by bullets. Walk around and you'll find another turret on a ledge. Portal yourself behind it and knock it over, then take the cube next to it and lay it on the button so that it's just barely pressing it down. It should be angled slightly off so that it doesn't block the center of the button. You'll be passing the pellet through here towards the door across the gap here, so that's why you need to do this.
With the cube set up, keep looking around for a white room with another button inside. When you find it, set the pellet portals up so that it can reach the doorway; one should be behind the cube's button, and the other obviously has to be where the pellet hits the ceiling. When that's done, walk onto the button in the lower room yourself and wait for the energy pellet to hit the receptacle past the doorway. You should be able to tell when it hits by listening for it. When it hits the receptacle, portal back up and get to the white wall next to the now closed door. The energy pellet will allow the floor here to sink down towards the elevator, but you'll have to stay sharp for a turret waiting for you. Quickly grab it and toss it into the emancipation grid so you can leave the chamber alive.
Still Alive 10
The main room of this chamber has two buttons in the center of the floor, and you'll need two cubes to lay them down. There's one on a high ledge, and by now you should know how to set up a momentum drop and switch it into a fling in midair. Take the cube and toss it to the ground, and then shoot a portal through the little window behind it. Drop down to the floor yourself so you can use the different-colored portal to get through to the room behind that window, and then set up your portals to be above each other, separated by a thin black line of tiles. You'll have to do what you had to do in an earlier chamber; step out of the top portal and either jump to the end of an electric grid or use a portal on the small white ceiling above it to get to the same spot. Run through to the other side when it's safe to do so, of course, and then put a portal down in the little crevice at the end and your other one through the little window opposite the crevice.
This next space is a lot bigger than the previous ones. Jump up some small black cubes in the stage and you'll find the second cube underneath a red barrier, as well as another white wall on the other side of the barrier. Simply portal the cube to the other side, and then follow it yourself. Just make sure you don't accidentally portal yourself into the barrier. The cube should have landed on a button that opens a door to the main room. To get the cube to the main room, shoot a portal into the main room, and then have your other one next to the cube. Having both cubes on the button will open the door to the elevator, but you'll have to jump over a little gap to get to it.
Still Alive 11
Still Alive 11 introduces spike ceilings that sink down from above, something you might have seen from trailer footage or something like that. This first room is extremely simple; just portal over to the other side and walk through the door on the other side before the spikes above you smash you. In the next room portal up to the little ledge between two spike ceilings, and then from there look for a window. Make a beeline for the window and portal yourself through to the other side. This room has a spike ceiling too, so you're not out of the woods yet; quickly put a portal up one of the walls as high as you can, and then walk through it after you can no longer see it so you land on top of the spike ceiling. If you were fast enough, you should be able to portal to another room by use of another small window. You'll know you're in the right place when you see a large piston moving back and forth.
Put a portal on the white wall next to the first piston, and then run to the wall that it crushes and put your other portal there. Run through it back to the start of the piston area and wait for the next piston to retract so you can rinse and repeat. Make sure you remember which portal is being used for the piston walls; you wouldn't want Chell to be crushed between two pistons thanks to a portal error. The last piston will have a white wall at the end like usual, but there'll be a window next to it too. Quickly put both your portals here and past the window so you can finally get to the elevator.
Still Alive 12
The first big room of the chamber starts off with two buttons and two turrets. You'll want to portal yourself behind the turret to the right of the door you come in from and take it down, then quickly get out of the way of the other turret's fire. Get to that one too, and you'll secure the room. There's a room to the side of the turret that leads up to a cube that you can get to with a white wall and a small momentum fling. The fling barely needs any momentum at all, and you can jump from the black tiles you're on into the white floor that the second turret used to be on. Once you have the cube, take it to the main room and leave it on the ground. Then portal yourself up to the top of the white platform nearby, and from there put the cube on the button so the platform can rise.
When the platform is all the way up, get ready to fling yourself upwards. Put a portal near the ledge to the left with the cube on it, and then have another one beneath you so you can jump into it. With the two cubes in your possession, you can now enter the next half of the level. The door you come across will get stuck, so you'll have to shoot a portal through the crack. You'll notice a turret's laser just past the portal; there's a white wall behind it, so you'll want to figure out where the turret is, shoot a portal behind it, and run backwards so you can fall into a little pit with some white walls. Use these to take out the turret, and then move yourself to the front of the malfunctioning door by using a single white panel. From here, you'll be able to see and get rid of another turret. There's a third one past this one, so get ready to shoot a portal behind it after you drop down to its level.
When the coast is clear, walk up a bright white hallway and do some maneuvering to get past an electric grid, and then make your way to a cube on a button. You'll want to leave this cube on the button and put your blue portal (for the sake of keeping track of them) next to it. Walk through the blue one and keep placing only your orange one to get back to the button that the two turrets used to protect, then walk through the orange to get the cube and bring it to this button. With the button active, portal up to the front of the broken doorway. You'll have to do a momentum fling to get to the elevator, which you can do with a high-up set of panels near you and a big drop to the side.
Still Alive 13
In the first room, look up for a small little hideout with a cube in it. Take it and bring it up to the ledge with a turret on it so you can knock it over, then use the cube as a shield as you ride a white platform up to the next ledge. There's a little button up here that fires energy pellets; pressing it once will get rid of the turret, and after it's gone you can use your cube to redirect later pellets into the receptacle on the wall across from you. The receptacle deactivates a barrier that you can crawl through, and you should bring your cube with you so you can put it on a button a little way down.
Put a portal behind the cube and then drop down to a turret, then quickly pick it up before it starts firing at you. Put your opposing portal on a white wall past the turret so you can grab the cube and take it to the next button nearby. Past this is a very long hallway consisting of a few turret alcoves and some rising/falling platforms. You shouldn't have any trouble getting through all of it. At the end is a much brighter room with a little button on it that opens the door leading to the elevator. In order to have enough time to get through the door, you'll need to place a portal in front of the door and another by the button. Then press the button, run towards the door and shoot a portal through it.
Still Alive 14
The last of the challenge maps is centered around cubes. There are five of them sitting around, and you'll want to take them all to the bottom of the chamber and use them to knock over the two turrets down there. The first thing you need to do is look up and find a tiny window in the ceiling. You'll need to fire through it at an angle, so you can drop one of the cubes through it onto one of the five buttons. Then do it again the other way and drop a cube on the second switch up there. After this, the energy pellet that moves back and forth here will move around very erratically. Shoot a portal straight up the window and try to redirect it to the receptacle at the start of the chamber.
With the pellet out of the way, another window will appear about halfway up the chamber. Shoot a portal through it and drop both cubes through the red barrier in there, and then turn around and fire a portal on a wall underneath you. When you meet up with your cubes, make sure one is on the button here and take the other through the next window. From here, take the cube to the last button and make your way back up to the main room of the chamber. The very last cube belongs on the big button in the middle of the chamber, if you haven't already figured that out. The door to the elevator will open with all five buttons pressed.
Test Chamber 13 (Advanced)
This will likely be your first taste into the advanced chambers. You'll notice right away in the starting room that there is no cube here. Stand on the button yourself and put a portal on the white square icon above the higher of the two buttons in the main room. Then drop down onto it yourself and redirect the energy pellet into its receptacle. You'll need to take the cube off the moving platform (which you can get to with portals, of course) and bring it to the lower button. To do this, take the cube to the closed door's platform and then jump to the button. Feel free to save all you want during this part of the chamber. When you do get the cube on the button, use the nearby wall to get yourself back on the top button to open the door to the elevator. Shoot a portal past the door and use the wall again to finish the chamber.
Test Chamber 14
And now, time to take a break from the special maps and replay Test Chamber 14 from the same menu. Select the portals used category and perform the same trick mentioned before; put a portal by the white platform in front of the elevator, and put another where the stairs retract into the ground. The par for a gold medal score is exactly 2, so it seems Valve became aware of this.
Test Chamber 14 (Advanced)
The skip won't be available for you in the advanced version. Run up the stairs to the left and put a portal on the floor next to the big black structure with the cube on it, then use the dropped staircase to fling yourself up to the cube. Take it to the button across the hall and get to the water-filled room before the energy pellet's room. The tricky part here is that there are no platforms for you to jump over, so you'll have to think ahead. Put a blue portal on the back wall of where you came from, and then put your orange one in front of the energy pellet. Walk through the orange portal so you can make your way back to the main part of the chamber, then put your blue portal up above the energy pellet's receptacle to finish the level.
Test Chamber 15 (Advanced)
For the start of this chamber, you'll need to fling yourself across with an infinite drop instead of a standard momentum fling. As for the energy pellet room, you'll need to redirect the pellet across each quadrant of the room since emancipation grids separate the room more than usual. After this is another fling room, but you'll have to work with the little room to the left more than usual. Put an orange portal up on the ceiling above the little drop in the side room, then run to the white floor by the next emancipation grill. You want to face away from the glass and put your blue portal on the ground. Then jump through, and as you fall to the floor, shoot your orange portal on the floor and hold so you can just barely land on top of the glass wall.
The next thing you need to do is redirect the energy pellet into the receptacle, but there are two ways around this. We'll go over the first one, since that actually involves getting the pellet into the receptacle. Take note of the glass wall between your room and shoot a portal on the side of it. There's a trick that will make things a lot easier; keep trying to shoot the other color portal at it, and if you do it right, it'll place itself on the other side of the glass. Then, to redirect the pellet, put a portal on the non-angled wall that the pellet hits naturally and another on the small piece of the wall between your first portal and the angled piece.
Alternatively, you can skip the energy pellet altogether with a different trick through the little hallway with the moving platforms activated by the pellet. Fire a portal down the hall and one on a wall next to you, then save your game. You'll want to inch yourself out of the portal so the reticle in the center of the screen lights up; this will let you know that you can shoot a portal again from where you are, and that's the first step to doing this right. When you can shoot a portal again, fire another one further down the hall with the same color that's already in the hall, and then quickly back out into the pellet room before the portal closes and reopens itself. Doing this wrong will send you into the water, so that's why you're encouraged to save beforehand. From the second position, you can shoot another portal into the last room of the chamber.
The last room is a bit trickier than usual, which is to be expected. Ride a platform up to one of the buttons and then look to the ceiling of the other button and put a portal up there. Put your other portal on the floor, press the button next to you, and then drop to the floor so you can press the other button. You'll then have to be quick about placing your portals on the wall and the floor to get the energy pellet to its receptacle before the doors close. This might take a few attempts, but at least the setup is easy to repeat as long as you don't accidentally drop off the sides of the button rooms.
Test Chamber 16 (Advanced)
All the turrets in this alternate map are caged and cannot be knocked over, meaning they'll always be active. To get past the first one, you'll have to portal yourself onto the top of its cage and crawl between it and the doorway to get by. You can then get past the next few turrets with simple portal movements until you get to the two cubes in front of the first Rat Man den. Since you can't knock these two turrets over, you'll need to put them both in the hall with some space for you between them. Then crouch and move the first cube over in front of the turret closest to you and lay it down, all the while making sure that the turret at the other end of the hallway isn't able to hit you with the other cube. When the first cube is in place, you'll be able to get to the second turret and put the second cube in front of it.
After these cubes are placed, use portals to get behind the two turrets in the next room, and from there you can get to the busted cube dispenser. Take all of the cubes in that room over to the twin-turret room, and then stack two cubes in front of the turret closest to the next room. After that, put two more on its left side to ensure that it won't hit you. With your remaining cubes, you'll need to inch your way into the final room like you did in the long hallway so you can put one of them on the button. Put a portal in the hall past the now opened doorway, and then slowly slink yourself and all of your cubes (including the one on the button) back into the twin-turret room. Save your game, and then take your cubes into the small area between the door and the space given to the second-to-last turret. Then crawl in there yourself and get a portal set up behind the turret. From there, you'll be able to safely get to the elevator since the last turret doesn't ever face you unless you decide to get in its way.
Test Chamber 17 (Advanced)
Instead of getting a companion cube for Test Chamber 17, you're given a sphere instead. And it doesn't even have a heart on it. The difficulty immediately becomes apparent after you try to scale the black ledges at the start of the chamber, since the sphere is obviously prone to rolling around. Blocking the energy pellets is a bit more difficult too, because instead of directly bouncing off a flat surface, they'll be erratically shot off into a weird angle since a sphere has infinite angles. Be sure to put your first portal on the wall that the first pellet hits before going into the pellet hallways to save some time, however.
The glass wall trick mentioned in Test Chamber 15 (Advanced) works in the main room of the chamber, and lets you skip all of the energy pellet receptacle puzzles. Look for the wall separating the main room from the final button of the chamber, and then fire a portal on the ground on your side of the glass. Then fire the opposite color into the first until it's bumped into the final button room. This speeds things up considerably.
When you make it to the main room of the level, look to the receptacle on an angled surface. There's a glass wall in front of where it usually goes now, but the solution to this is actually pretty simple. Put your exit portal on the ceiling above the other angled surface, and the pellet will bounce into the receptacle with ease. As for the energy pellet in a small black room, there's a glass wall in here too. Fortunately for you, you should be able to get the pellet to its receptacle by merely holding your sphere up to the dispenser so that it redirects upwards and in the direction of the receptacle.
The last pellet receptacle is more similar to the original chamber design, except both door buttons are on higher ledges as opposed to just one. There are two ways around this. The first is the normal way, which is to put your sphere down so you can jump from it to the button that controls the front door. When the pellet hits the second door, jump off your button so that the pellet is trapped between the doors, and then quickly take your sphere to the other button to let it into the receptacle. The other way is more time consuming but easier on your patience. Check the Rat Man den for a bunch of cameras that you can use to pile on top of each other so you can jump to a button without the sphere. This will allow you to put the sphere on its own button, which in turn results in being able to have both doors open at once.
When you've activated the platforms, get to the next room as per usual, which is already different in itself since this room didn't exist before. The last room is a simple momentum fling puzzle, which makes you wonder why they bothered with it in the first place. Get through it and use the sphere to go through the euthanizing process so you can get to the elevator.
Test Chamber 18 (Advanced)
As you may recall, this chamber is separated into three areas. There's the first one, which isn't special, there's the turret room, and there's the momentum room at the end. The first area is a lot more tedious to get through than before. In order to get to the next platform, you need to set up a momentum fling using the wall above you and the white tile below. But, to make things even worse, you need to also fire a portal at the floor of the next platform while being flung, since there's no other way to get up there now. If you can pull that off and can safely get to the platform you shot your portal onto, then the hard part is over. Look underneath the next platform for a little black block sticking out of the wall, and then portal yourself on top of it. From here, you can use the white walls in view to get to the turret room.
The turret room is especially bothersome now; the energy pellet is gone, and you'll need to physically get to each turret and manually deactivate them. The first one you should go for is the one to the far far right, which will be the one closest to a wall Save, and then shoot a portal next to it. Put another one for you somewhere nearby, and then jump to the turret and take it back to a safe place before the others shoot you to pieces. Try to save this first turret, because you can use it to knock over the next turret. The "next turret" will be the one facing in the direction of the cube. Save again, put a portal high up above the turret on a wall, and put another portal underneath the turret you have. Hopefully you knock it over on your first try, but if not, then you can use the save you (should have) made before making your attempt. The third turret will be the higher up of the two remaining ones. Put a portal up above the turret's platform and put the other one next to you, then save before trying to jump to it. When you stick the landing, toss the turret into the water and put a portal on the floor near the last turret. Then look left (towards the cube) for a small white floor just barely above the water. Save again and use the drop to fling yourself high in the air, which will just barely give you the horizontal distance you need to get to the last turret. If any of this was too confusing, you might want to just watch the video on it.
As for getting to the cube, ride the platform to the little button like with the standard chamber. The momentum fling you set up to get to the cube is different this time, however, and it's once again suggested that you save beforehand. When you press the button, put a portal on the slanted panels that come out of the wall, and then use another on the white floor below you. When you first fling yourself you'll be sent back into this white floor, so you'll essentially have to do a double-fling in order to get the distance necessary to reach the cube. Take it and walk off the ledge just slightly and walk backwards while in the air so you can land by the little button below to save time, then hit the button again and use portals to quickly take the cube back to the large button it's supposed to be on. The last room with the momentum drops is exactly the same, so there shouldn't be too much trouble getting to the elevator.
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