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Test Chamber Walkthrough

Portal has 20 test chambers (numbered 00 through 19) followed by an escape sequence and a boss fight. The chambers are grouped by the mechanics they teach. This walkthrough covers every puzzle solution, grouped by difficulty phase.

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If this is your first playthrough, try each chamber yourself before reading the solution. The puzzles are designed to be solvable through observation, and the satisfaction of figuring them out is the best part of the game.

Phase 1: Learning Portals (Chambers 0 to 7)​

These chambers teach you what portals do. You start with no tools and gradually gain the portal gun.

Chamber 00​

You wake up in a relaxation vault behind glass. A portal opens on the wall. Walk through it to exit the vault. That is the entire puzzle. GLaDOS introduces the concept of testing and the Aperture Science Enrichment Center.

Chamber 01​

A pit separates you from the exit. An orange portal sits on the far wall, and a blue portal opens on your side. Walk through the blue portal and exit through the orange portal on the other side of the pit. Still just teaching you what portals look like.

Chamber 02​

You pick up the portal device. This restricted version fires only blue portals. Orange portals are pre-placed by the facility.

Fire a blue portal on the wall across the pit, then walk through the orange portal already placed behind you. Cross to the exit.

Chamber 03​

Two rooms separated by glass. Fire a blue portal into the second room through the glass (you can shoot through the window), then walk through the pre-placed orange portal to enter the second room. Reach the exit.

Chamber 04​

First introduction of the Weighted Storage Cube and floor buttons. Pick up the cube from the platform, carry it down, and place it on the button. The door opens. Walk through to the exit.

Chamber 05​

Combines cubes, buttons, and portals. A cube sits on an elevated platform you cannot reach by walking. Fire a portal onto the wall behind the cube, walk through, grab the cube, return through the portal, and place the cube on the button below.

Chamber 06​

Multiple rooms with pre-placed portals. You need to use a cube in a different room than where you find it. Carry the cube through a portal to the room with the button.

Chamber 07​

Introduces the High Energy Pellet. An emitter fires a pellet that bounces around the room. A receptor on the wall needs the pellet to power the exit door. Place a blue portal where the pellet hits the wall, and let it redirect through the pre-placed orange portal into the receptor.

warning

The pellet kills you on contact. Do not stand in its path while setting up your portals. Watch its bounce pattern first, then place portals between bounces.

Phase 2: Momentum and Complexity (Chambers 8 to 14)​

These chambers introduce momentum, Unstationary Scaffolds, and multi-step puzzles.

Chamber 08​

First true momentum puzzle. A pit with a portal on the floor and a portalable wall across the room. Drop into the pit, fall through the floor portal, and launch out of the wall portal to cross the gap. This is your first fling.

Chamber 09​

Builds on Chamber 08. A deeper pit and a longer gap. You need more speed, so the pit is deeper. Same fling technique, bigger scale. GLaDOS starts noting that you are ahead of schedule.

Chamber 10​

Two-part puzzle. First, route a pellet into a receptor using portals. This activates an Unstationary Scaffold. Ride the scaffold to an elevated area, then fling across a gap to reach the exit.

Chamber 11​

You receive the full portal device. Both blue and orange portals are now under your control. The chamber is a simple test of placing both portals yourself. Put one portal on a lower wall and one on an upper wall, then walk through to reach the exit elevator.

This is where the game opens up. Every puzzle from here forward assumes you control both portals.

Chamber 12​

A large room with a floor button and a cube behind a Grill. The cube is on a raised platform in a separate area. Portal to the cube, grab it, and portal back. Place the cube on the button. Watch out for the Grill placement. You need to bring the cube around it, not through it.

Chamber 13​

First multi-step puzzle. An Energy Pellet needs to be routed into a receptor, which activates a platform. Ride the platform to a second area where a cube and button open the exit. The pellet routing requires two portals placed at specific angles.

This chamber is also the first one available as an Advanced Map and Challenge Map after you complete the game.

Chamber 14​

Introduces the concept of portaling to places you can see but cannot walk to. A large room with catwalks at different heights. Place portals on walls to reach each level. A cube at the top must be brought down to a button at the bottom.

Phase 3: Hazards and Turrets (Chambers 15 to 18)​

The difficulty ramps up. Turrets appear, chambers get larger, and the puzzles combine multiple mechanics.

Chamber 15​

The double fling chamber. A two-stage momentum puzzle where you fling from one pit into a second pit, building speed, then fling a second time to reach a distant platform. This is the hardest pure physics puzzle in the main game.

Solution:

  1. Place a portal on the floor of the first pit and a portal on a high wall aimed at the second pit.
  2. Drop into the first pit. You fling out of the wall portal and land in the second pit.
  3. While falling into the second pit, quickly replace one of your portals to the floor of the second pit.
  4. The other portal should be on a wall facing your final target.
  5. You exit the second fling with enough speed to reach the exit platform.
tip

The trick to Chamber 15 is portal replacement speed. You need to swap one portal's position during the brief time you are airborne between pits. Practice the timing. If you overshoot or undershoot the second pit, adjust the height of your wall portal.

Chamber 16​

First turret encounter. Three turrets guard the path to the exit. You have cubes available and full portal access.

Approach:

  1. Scout the turret positions through a portal. They face the main corridor.
  2. Place a portal behind the turrets and another on a nearby wall.
  3. Walk through and tip each turret from behind.
  4. Alternatively, place a portal on the floor beneath a turret. It falls through and is disabled.
  5. Clear all three, then walk to the exit.

Chamber 17​

The Companion Cube chamber. This is the longest test chamber in the game and involves multiple floors, Energy Pellet routing, turret encounters, and platform puzzles. You must carry the Weighted Companion Cube through the entire chamber, using it on buttons to open doors and as a shield against turrets.

Key steps:

  1. Grab the Companion Cube from the dropper.
  2. Use it on the first button to open the ground-floor door.
  3. Navigate through a turret corridor by carrying the Cube in front of you as a shield.
  4. Route an Energy Pellet into a receptor to activate the elevator.
  5. Ride the elevator up with the Cube.
  6. Use the Cube on the final button, then retrieve it.
  7. At the end of the chamber, GLaDOS tells you to incinerate the Cube to proceed. Drop it into the incinerator. The exit opens.
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You cannot skip the incineration. The door does not open until the Companion Cube is destroyed. GLaDOS comments on how quickly you did it.

Chamber 18​

The hardest test chamber. Multiple turret arrays, Energy Pellet routing, and a multi-level structure. You need to clear turrets, route a pellet, activate platforms, and fling to the exit.

Key sections:

  1. Turret gauntlet. Three sets of turrets in a corridor. Use portals to get behind each group and knock them over.
  2. Pellet puzzle. Route the pellet through two portal redirections into a receptor.
  3. Platform section. The activated receptor powers a moving platform. Ride it to the upper level.
  4. Final fling. A momentum fling from the upper area to the exit elevator.

Chamber 19 and the Escape​

Chamber 19​

The final "test." GLaDOS instructs you to lie down in a relaxation position as you ride a platform into a furnace. She thanks you for participating and promises cake.

You are not supposed to comply.

Escape the furnace:

  1. As the platform moves toward the fire pit, look to the side for a portalable wall.
  2. Place a portal on the wall and another portal on any reachable surface behind you.
  3. Step through the portal before the platform drops you into the fire.
  4. You are now behind the scenes in Aperture Science's maintenance areas.

The Escape Sequence​

The maintenance areas are a sharp contrast to the clean test chambers. Rusty pipes, abandoned offices, concrete corridors. No more chamber numbers. GLaDOS is aware you escaped and alternates between threatening you and trying to lure you back.

What to expect:

  • The walls are mostly concrete and accept portals, but not all surfaces work. Look for light-colored patches.
  • Turret ambushes appear in tight corridors. Listen for the "deploying" sound and scout with portals before walking in.
  • Hidden rooms contain graffiti from a previous test subject. These tell a backstory about Aperture Science and someone who survived before you. "The cake is a lie" comes from here.
  • The escape has three main sections: maintenance tunnels, a turret gauntlet, and a piston room.
tip

Look for Rat Man dens. The previous test subject left drawings and notes in hidden rooms throughout the maintenance areas. They add lore and are some of the most memorable visuals in the game.

The GLaDOS Boss Fight​

You reach GLaDOS in her central chamber. She is a massive AI unit suspended from the ceiling. A rocket turret is mounted on the wall.

How to win:

  1. GLaDOS releases neurotoxin. A timer appears. You have exactly five minutes (300 seconds) before the toxin kills you. GLaDOS announces the countdown explicitly. If the timer hits zero, you die instantly regardless of position or health.
  2. A rocket turret targets you with a red laser. Position yourself so GLaDOS is between you and the turret.
  3. When the rocket fires, dodge. The rocket hits GLaDOS and knocks off one of her personality cores.
  4. Pick up the fallen core and drop it into the incinerator in the room.
  5. Repeat for each core. GLaDOS has four personality cores in total.
  6. After the final core is destroyed, GLaDOS deactivates. An explosion blasts you to the surface.

Tips:

  • Use portals to redirect rockets. Place one portal in the rocket's flight path and another portal aimed at GLaDOS. The rocket passes through and hits her on the other side. This is the intended way to fight her.
  • Between core drops, GLaDOS taunts you and deploys additional turrets. Clear them as they appear.
  • The neurotoxin timer is tight but manageable on a first playthrough. Do not panic. Focus on portal placement.
danger

Do not stand still during the fight. The rocket turret fires continuously, and the homing rockets will catch you if you stop moving. Keep circling GLaDOS while waiting for shots.

After the Credits​

After defeating GLaDOS and watching the ending, the credits roll with the song "Still Alive." Once the credits finish:

  • Advanced Maps unlock. Six test chambers (13 through 18) with harder layouts.
  • Challenge Maps unlock. The same six chambers with medal targets for Least Portals, Least Steps, and Least Time.
  • Commentary Mode unlocks. Replay the game with developer commentary nodes explaining the design decisions behind each chamber.

For a full guide to the post-game content, see Advanced Maps and Challenges.

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The original 2007 ending faded to white after GLaDOS was destroyed. In March 2010, Valve patched the ending to show Chell being dragged back into the facility by an unseen robot (the "Party Escort Bot"), connecting Portal directly to the opening of Portal 2. If you are playing today, you will see the updated ending.