Portal/Chamber 16

This chamber introduces you to turrets, which will open fire on you if you enter their line of sight. You can take some damage from their bullets before you die and this damage will heal in a few seconds once you escape their fire. Getting shot at by multiple turrets at the same time is something to avoid. "Due to mandatory scheduled maintenance, the appropriate chamber for this testing sequence is currently unavailable. It has been replaced with a live-fire course designed for military androids."

- GLaDOS

Walkthrough
Three turrets may try to shoot you through the glass as you enter, but luckily the glass appears to be bullet-proof. The first turret is facing away from you, and as such it can be disarmed easily. You can pick it up and toss it onto the ground, or place a portal under it and let it fall through to wherever you place the other portal. As long as it is no longer on its feet, it will shut down.

The next turret will be noticeable with a red laser beam pointing against the wall. Quickly fire a portal behind it, and pass through a new portal of your own. You could also disarm it by shooting a portal underneath it.

You may notice at some point that you have less time from when a turret sees you to when it shoots you if the turret just recently saw you as well. If you wait for the turret’s laser to stop moving around, you will have more time in its line of vision to act before it starts shooting.

An alcove containing a turret is next. Since you can't shoot a portal under it, you can instead create one on the red X painted above, and drop another turret or camera on top. Alternately, place a portal behind the turret, as with the last one, and knock it over yourself.

You may wonder at this point why there was such an obvious X hastily painted just in the right location. As you walk to the next area, you will notice two cubes behind a panel, and the word “help” drawn on the floor. Removing the cubes, notice that there is actually an additional area that you can crouch and crawl into. This is by no means a required area, but the scribblings add some important questions to the storyline. It also gives indications that all of this testing may not be as innocent as it initially seemed to be.

Two turrets are now covering the corridor. To get rid of them, you need to open a portal on the red X above each turret, and drop a weighted storage cube (or other object) onto the turrets.

Two turrets cover the next room, but you can sneak a portal behind them without too much difficulty. Then enter the side room, where you will find a malfunctioning cube dispenser, which gives you a lot of objects to toss at your next set of obstacles.

The button room contains three turrets, with a red X marked over each one. You can disarm one of them with your portals, and use the set of storage cubes to drop them on the turrets. Place a cube on the red button to open the door.

The exit is blocked by some fencing and a couple turrets, however you can still shoot portals through the fences (being sure to avoid turret fire), shut down the turrets, and proceed to the chamberlock.

Advanced
In the advanced chamber, all turrets are enclosed in metal cages from which they can shoot outwards while remaining untouchable. No picking them up, no hitting them with objects, and no portaling them somewhere else with portals beneath them.

For the first turret, you will have to portal yourself on top of the cage, crouch to get through, and quickly move around the corner. Next, place a portal on the wall behind the second turret, and walk on through. Then skip the third turret completely by simply placing a portal on the far wall.

Now is when things really get tricky. You will likely have to use cubes to prevent the line of sight between the turrets and you. If you need more obstacles than the provided cubes (you shouldn’t though), in the side room with the writing there are many brown boxes that, while you cannot pick them up, can be pushed and portaled elsewhere. While crouching behind a cube, the turret will not be able to see you, but if you pick the cube up while crouched it will, although the cube will block most of the bullets.

Place a cube on either side of you, and crouch walk until just before one of the turrets will see you. Move the cubes to a better placement, and continue. When you can, portal into the next area behind the next two turrets. Now portal into the cube room. Once there, place a portal back on a high wall where you came from, and the other portal under the various cubes, as you may need a lot of them. Head back over and get ready for the last room.

The first (relative to the entrance) turret in the room you are currently in will not be a worry, but put two cubes stacked in front of the second turret so that you don’t have to worry about it much (be careful though, as there may be a small angle where it can still shoot you). As you enter with cubes in front of you into the last room, try to get one between you and each turret as you move. You can also get the edge of a cage between you and a turret’s eye so that it will not be able to see you. Place a cube on the button so that the door opens. Place one portal on a wall just on the other side of the door, and then take the cube back off of the button so that the door closes. Now back track to safety and place the other color portal on a wall so that you have access to the other side of the door.

Before entering, be sure to know which way you will be shooting your next portal, as you will only have a brief time before you are shot. Enter and immediately portal behind the turret. Then place a portal as far down the exit hallway as you can, and come on through, moving as necessary to not be shot, and then exit.

Portals
Which turrets you take out by hand as opposed to with portals is very flexible here, but here’s a possibility: Take out the first turret by hand.
 * Bronze at 9 portals
 * 1) Blue portal behind the second turret.
 * 2) Orange portal in an accessible location. Go through behind the second turret (take it out if you wish). Run past the third turret to the two turrets facing each other.
 * 3) Blue portal on the X above the far turret.
 * 4) Orange portal on the wall or floor. Drop a cube onto the turret. Take out the near turret by simply running to it and picking it up before it shoots.
 * 5) Blue portal on a ground-level wall behind the two turrets in the next room. Go back to the existing orange portal to come up behind them and take them out manually.
 * 6) Orange portal on X above the turret facing the entrance in the button room. Drop a cube through. Take out the one facing away manually.
 * 7) Orange portal on X above the third turret in the button room. Backtrack and drop another cube through. Place a cube on the button.
 * 8) Orange portal at ground level behind turret guarding this next door. Backtrack to existing blue portal and come through.
 * 9) Blue portal somewhere in the final room. Come through and take out the final turret.

Again, flexible, but here’s a likely scenario: Take out the first turret by hand.
 * Silver at 4 portals
 * 1) Blue portal behind the second turret.
 * 2) Orange portal in an accessible location. Go through behind the second turret (take it out if you wish). Run up and grab the third turret before it shoots.  At this point you have many cubes that you can use as shields between you and turret fire. It is a little bit like proceeding in the advanced chamber, except with the advantage of being able to get rid of a turret once you reach it. Remember to crouch, and you should never need more than two cubes at a time. Take out all the turrets up to and including the ones in the button room. Place a cube on the button.
 * 3) Orange portal at ground level behind turret guarding the door. Go way back to the existing blue portal and come through.
 * 4) Blue portal somewhere in the final room. Come through and take out the final turret.

Take out the first turret by hand, but pick it back up after it’s dead. Use it as a half-shield, and toss it at the second turret when you are close enough. From here, proceed as in the silver method until you have the button pressed. Notice that you can actually see the second fence through the first fence.
 * Gold at 2 portals
 * 1) Blue portal through both the first and second fences.
 * 2) Orange portal anywhere you can get to. Go through and exit.

Steps
Picking up a turret as it’s dying helps prevent being accidentally shot. You might try using floor portals to move a cube somewhere where it will help block the line of sight between where you want to go and a turret.
 * Bronze at 70 steps
 * Silver at 55 steps
 * Gold at 40 steps

Time
Times unfortunately include the 20-second monologue at the beginning of the map.

This challenge is mostly just about getting really good at shooting portals quickly and getting rid of turrets as easily as possible. It’s really nerve-wracking because you don’t have time to get rid of all the turrets, so you end up being shot at quite a bit. Stick to it!

Here is one possible gold method. Shoot a portal on the ground at the door while you wait for the door to open. As soon as it does, shoot one at the top part of the wall so that you fall through, probably knocking over the turret in the process, and can easily continue on. Put a portal behind the next turret, and then across the next hallway. Now for the two turrets facing each other, place a portal on the X above the nearest one (this should be happening around the 30 second mark). Walk towards the two cubes and shoot a portal underneath them so that one falls through to knock out the turret, but grab the other before it falls. Then just use it as a shield as you run towards the other turret. When you are close enough, toss the cube at the turret, and quickly shoot a portal at the far corner of the next area, coming on through. Place a portal on the wall behind the turret in the button room that can probably see you right now, and another on the floor below the turret (in that same room) that is actually on a portalable floor. This will hopefully knock out both of these turrets. Now put a portal underneath you so you come out the other floor portal. Quickly run onto the button, shoot a portal on a wall past the first fence (past both fences if you get lucky), and come through before you die from the third button-room turret. Proceed to the exit (another portal past the second fence if necessary).
 * Bronze at 1 minute, 10 seconds (70 seconds)
 * Silver at 1 minute (60 seconds)
 * Gold at 52 seconds

No Cheating SpeedRun in One Segment for Mere Mortals
To complete this chamber quickly, you need to take some damage from the turrets. Knocking them down just takes too much time and you can't hide from them all. For the time challenge, if you die it's no big deal to try again. But in a single segment speedrun you need to have a way to get through quickly with very little chance of getting killed. As a result, you may need to accept a slightly poorer time for this chamber.

While you're waiting out GLaDOS's speech, stand near the door and put a portal under your feet. Practice this and adjust your position so that as soon as the door opens you can put the other portal high on the right-hand wall and fall through, getting a boost towards the first turret. As you pass the turret, pass close enough to knock it over and continue. You can pick it up and throw it if you like, but don't lose any time. When you see the second turret, put a portal behind and to the right of it. Move to the left as you continue to advance, place a portal to the left of the doorway and walk through, bypassing the turret. Now turn to the left, place a portal high up and as far right as possible on the wall at the far end of the corridor. Put the other portal under your feet and fall through.

This brings you to the first of the two turrets facing each other along a long corridor. Turn to the left and advance just until you can put a portal over the "X" mark on the ceiling above the turret behind the glass partition. Pull back immediately; this is the first place where you can get yourself killed. The portal needs to be fairly accurately placed, but don't stand there getting shot at. Try to get this right on the first attempt, but if you have to move the portal, well, that's better than being dead. Put the other portal carefully under the bottom of the two cubes. Again, accurate placement is important, otherwise the cube will not fall straight and may miss the turret. If it does miss, you can try again with the other cube. Ideally, you want to be confident enough that while the cube is falling you are already advancing again into the corridor to put a portal over the turret at the other end. This time, put the portal close to the far wall and towards the left because you're going through it yourself and you want to land out of sight of the turrets in the first large room. If you're brave, after placing that portal, immediately place the other under your feet and fall through, escaping the turret's bullets. If this doesn't reliably work for you, it's best to pull back out of the turret's sight before you place your own portal. Either way, land behind the turret and out of sight of the large room.

Now for the third brush with death. Advance from your hiding place, across the danger zone where you will get shot at by one of the turrets in the large room, and reach safety behind the glass panel. This sounds easy enough, but there are two things that you need to accomplish on the way. First, knock down the turret near which you landed. Passing close enough to tip it over is fastest, or pick it up and throw it if you prefer. Note that you can get unlucky and have a thrown turret land on its feet again and start shooting you. If this happens, you will be dead. Second, as you pass the opening to the large room, you need to get a portal onto the wall of that room, right in the opposite corner. On the long wall on the left side is best, under and to the right of the observation room, but if it lands on the furthest wall, just work with it. What you don't want so much is to have the portal on the long wall but not right in the corner. Once you're safely behind the glass panel, put the other portal in the wall nearby and walk through. You are now in the first large room, looking through the doorway into the second large room with three turrets and a button (if your portal was on the furthest wall, you will need to turn to the left). You can see one of the turrets. Put a portal underneath it. Ideally, you want to use the color of the portal close by so that the turret will fall out of the portal you left on the other side of the glass panel. If you use the wrong color, the turret may fall into you, but this will probably be manageable.

A word is due at this point about the two turrets in the first large room. As long as you don't move away from the long wall you'll be out of their sight and they won't bother you. You can't drop them through portals because they are standing on a non-portalable area of the floor. If they make you nervous, you can try dropping the first turret from the next room on the head of the closest one (the furthest one is less likely to see you), but it's best to remember to stay far back and just ignore them. Anything else will just take up more time. Now for the turret that's against the far wall of the second large room with the button. The reason we came into this room right in the corner is so that we would be hidden from it by the edge of the doorway. Now we need to move to the right (but staying back) until we can put a portal in the wall behind it. Put the other portal in the wall to your left and walk through. Now you're in the room with the button, uncomfortably close to, but behind, a turret. This is not where the danger is coming from. Turn to your left where you will see the third turret in this room taking aim or perhaps already shooting at you. Put either portal on the wall above it under the camera. The camera will fall on the turret and knock it over, but don't wait for this to happen; keep going. Either pick up and toss away the turret right by you or, as before, save time by brushing past it and knocking it over.

You don't have a cube to put on the button, but that's OK because you're going to stand on it. The door to the next room will open. Move to the right edge of the button, as you face the next room, so that you can see along the right-hand wall. You want a portal not in the next room, not even behind the grating where the turret is, you want the portal in the room beyond and to the right of that, i.e. the room with the exit chamberlock. It's hard to describe exactly where this is, so play the chamber, save the game at this point and look for and remember the right spot. When you have that portal in place, put the other portal close by (perhaps in the floor) and go through. Disregard the last turret. Move and turn left until you can see down the short corridor to the chamberlock. Place a portal on the wall just outside of it, place the other on the wall where you stand, walk through, turn right and go into the chamberlock.

Expect your time from the opening of the entry chamber lock to arriving in the exit chamber lock to be about sixty seconds (the silver time challenge; you can reach 52 seconds for gold, but it's very hard to do reliably). The first twenty two seconds were wasted listening to GLaDOS.