How this guide is built: Portal is short and linear, so a walkthrough is genuinely useful when you stall — but it is also a game designed around creativity, where (as the StrategyWiki guide itself stresses) the “expected” solution is almost never the only one. So this guide does two things. It opens by teaching the six mechanics every chamber is built from, because once you understand portals and momentum you can solve rooms your own way; and it then walks every chamber as one workable path in our own words, surfacing the genuinely tricky timing and the boss fight in detail. Read the mechanics first and the test chambers stop being locks and start being toys. Facts are cross-checked against the official Steam page (app 400), a full text walkthrough, the StrategyWiki guide and the official Valve trailer.
What is Portal?
Portal is a $9.99 first-person puzzle game by Valve, released on 10 October 2007 as part of The Orange Box and sold standalone ever since. You play Chell, a silent test subject woken in the Aperture Science laboratories and herded through a series of test chambers by a passive-aggressive AI called GLaDOS, who promises you cake at the end. Your only tool is the Aperture Science Handheld Portal Device — a gun that paints two linked doorways, one blue and one orange, onto the world. Walk into one and you step out of the other.
That single idea unfolds into one of the most acclaimed games ever made. It is built on the Half-Life 2 engine, grew out of a student project called Narbacular Drop, and is as famous for its writing, its turrets, the Weighted Companion Cube and the end-credits song “Still Alive” as for its puzzles. The campaign is roughly three hours long: twenty test chambers (numbered 00–19), then an escape through the facility’s rotting backstage, then a confrontation with GLaDOS herself.
The six mechanics every chamber is built from
Portal teaches you one idea at a time and then combines them. Learn these six and you will recognise every puzzle as a remix of things you already know.
| Mechanic | What it means — and how to use it |
|---|---|
| Portals & line of sight | Blue and orange are two ends of one hole — there is no “other dimension.” If one portal is open and cloudy, its partner isn’t placed yet. The trick is to look at a far wall and shoot a portal there, then step through your near one to teleport across. |
| White vs. metal surfaces | Portals only stick to white concrete. Metal, glass, grates and moving panels are portal-proof. When you’re stuck, the level is telling you where you can shoot — scan for the white surfaces. |
| Momentum (the “fling”) | GLaDOS says it best: “speedy thing goes in, speedy thing comes out.” Speed is conserved through portals. Fall into a floor portal and you rocket out of a wall portal. Put a portal on a high wall and one on the floor far below, then fall in to fling yourself across big gaps. |
| Cubes & buttons | Big red floor buttons need weight. Drop a Weighted Storage Cube on one to hold a door open while you go elsewhere. Cubes also block bullets and energy pellets, and a destroyed cube is re-dispensed where you found it. |
| Energy pellets | An emitter fires a bouncing ball of light; land it in its receiver to power something permanently. Use a portal to redirect the pellet’s path. Touching a live pellet kills you, so mind where it bounces. |
| Turrets | Sentry guns with a narrow vision cone (watch their red beam). They knock you back when firing, so you can’t walk up from the front — portal in behind them and tip them over. They won’t shoot each other unless you trick them into it. Rocket turrets are slow, kill in one hit, and can’t be destroyed — only exploited. |
One more habit worth building early: passing through a force field deletes both your portals, so place them after you cross, not before. And the Material Emancipation Grid at each chamber exit vaporises any cube you try to carry out — cubes are single-room tools.
How to read the chamber notes below
Each chamber gets one workable solution, written so you can stop the instant the idea clicks. Where the game is really teaching a new mechanic, that’s flagged. Remember the StrategyWiki point: these are not the answers, just an answer — if you find a cleverer route, that’s Portal working as intended. Chambers 00–09 use limited portals; from Chamber 11 you control both, and the difficulty climbs.
Chambers 00–09: learning the tools
- 00 — Prelude. Walk through the pre-placed portal, pick up the cube, drop it on the button, ride the lift. You’ll see the exit’s Emancipation Grid — that’s why you can’t carry cubes between rooms.
- 01. The portals you can’t place yet cycle through different rooms on a timer. Wait for the far portal to show the cube room, grab the cube, wait for it to show the button room, and post the cube onto the button.
- 02 — you get the portal gun (one colour only). Drop through the pre-placed portal, pick it up, then shoot a portal onto any white wall to reach the exit.
- 03. Use single portals to cross two gaps. From here on you can also destroy security cameras by opening a portal behind one — do all 33 across the game for Camera Shy.
- 04. Shoot a portal onto the floor under the cube dropper, collect the cube from the exit portal, drop it on the button.
- 05. Two buttons. Portal under the cube to retrieve it, place one cube on each button, then portal up and out.
- 06–07 — energy pellets. Place a portal so the emitter’s pellet is redirected into its receiver (06 puts it on the ceiling above the receiver; 07 captures the pellet from across the room and rides a moving platform out).
- 08. A more precise pellet relay over a deadly floor: catch the pellet with one portal, send it to the receiver with the other, then portal onto the moving platform.
- 09 — the “impossible” test. GLaDOS insists it’s broken; it isn’t. Portal under the cube to drop it through, send a portal through the gap above the force field, retrieve the cube and put it on the button.
Chambers 10–12: momentum and the fling
This is the turning point of the whole game.
- 10. The first momentum lesson. Wait for the far portal to appear high behind you, shoot the floor below, then jump (don’t just step) in — you fly forward out the other side. Repeat with deeper pits to feel how the portal preserves your forward speed.
- 11 — the dual-portal upgrade. Cross using single portals to ride a platform to the centre, then grab the upgraded gun. From now on you place both portals yourself.
- 12 — the fling. Put a portal on a far wall over a pit and one on the pit floor, then fall in to be flung up to a high ledge. Each step uses a higher, further wall portal — including a 45° angled wall that flings you diagonally — until you reach the cube, drop it on the button, and leave.
Chambers 13–15: the long puzzles
These combine everything — pellets, cubes, moving platforms, and flings — into multi-stage rooms. They’re where players first feel genuinely stuck, so here are the shapes of the solutions:
- 13. A two-room pellet-and-cube relay. Get a cube onto a button to open the gate, then route a pellet into its receiver, then ferry the cube through portals between two buttons (“post” it through a ceiling portal onto each one-dot then two-dot button) to open the way out.
- 14. A vanishing staircase teaches timing: shoot a wall portal, wait for the stairs to disappear, portal the floor where they were, and fling to the cube. Then cross hopping moving platforms the old-fashioned way and finish a pellet into its receiver.
- 15 — the marathon. Several force-field gates, each crossed by repeatedly re-shooting the floor portal under yourself as you fall to build enough speed to clear the field. Between them are pellet relays (remember: crossing a force field wipes your portals, so place them after) and a backwards moving-platform maze over deadly floor. Slow and fiddly, but each piece is a mechanic you already know.
Chamber 16: turrets, and the Companion Cube ahead
16 swaps puzzles for a “live-fire course” of turrets. The method is always the same: get a portal onto a white wall behind a turret, step through, and tip it over from the side — or drop a cube on its head from a ceiling portal. Where two turrets face each other, you can dodge so one shoots the other and unlock the Friendly Fire achievement (you’ll hear them apologise). Hide behind glass and corners to break line of sight while you set up each shot.
Chamber 17: the Weighted Companion Cube
The chamber hands you a heart-marked Companion Cube and asks you to keep it through a room full of energy pellets. Use it as a shield: hold it in front of you down the pellet corridors, wait for a pellet to fire before entering so you don’t get shot in the back, and use it to deflect pellets into receivers. You’ll also stack it to climb stairs and stand on buttons. At the end, GLaDOS demands you drop the cube into the incinerator to continue — doing so is required, and earns the grimly-named Fratricide achievement. (Yes, it’s a famously sad moment. The cube cannot, the Enrichment Center reminds you, actually feel pain.)
Chambers 18–19: the last tests
- 18. A big room with four turrets around a rotating pellet emitter — redirect the spinning pellets to knock the turrets out (trial and error on the angles). Then a precise sequence: press a button to open a receiver door just as a pellet arrives; fling off a 45° wall into a cube chamber; ferry the cube across moving walls onto a button. The chamber ends with a bouncing portal-climb — drop into a floor portal, and as you bounce up out of a higher one, shoot the next platform’s surface, climbing by alternating portals. Don’t touch the movement keys mid-bounce, and remember the spinning screen doesn’t move your actual aim.
- 19 — the final test. A pellet bounced off 45° walls into its receiver, then a careful ride on a moving platform — including standing “inside” a portal-proof blocking wall to let the platform carry you the last stretch … straight toward an incinerator. The reward, GLaDOS reminds you, is cake.
The escape: there is no cake
At the end of Chamber 19 the platform carries you toward an incinerator. Don’t burn. Put a portal above the fire and one on a side wall and fling yourself to safety — GLaDOS’s cheery façade cracks, and you escape into the facility’s backstage. From here the game becomes a long, atmospheric chase through maintenance areas: piston rooms, fans you portal past by timing a shot through the blades, secret graffiti dens scrawled by a previous subject, and turret traps you defeat exactly as before — portal in behind, push over. You’ll meet your first rocket turret; it’s slow and one-hit-kill, so just make it fire to shatter the glass between you, dodge, and move on. Keep following the painted arrows and “fling” up the structures until you reach GLaDOS herself.
The GLaDOS boss fight
The finale is a two-stage puzzle, not a shooter. When you arrive, GLaDOS drops a strange object and spends a long monologue begging you not to touch it. Touch it.
- Burn the Morality Core. Place a portal near the room’s incinerator and another on a wall by the armored control booth so you can sprint between them. Press the button to open the furnace, grab the object GLaDOS dropped — her Morality Core — and throw it in. This is what was keeping her from flooding the place with neurotoxin, so now a ~6-minute countdown begins.
- Three hits, three cores. A rocket turret now guards the room. Each hit on GLaDOS is the same trick: put a portal under GLaDOS and another on a wall in the rocket’s path, line yourself up so the rocket flies into your wall portal and out under her, then dodge. Each hit knocks a personality core loose; pick it up and incinerate it like the first.
The three cores sit in awkward spots you reach with portals:
- Curiosity Core — on top of some pipes; portal the wall behind them and reach through.
- Knowledge Core — on a fin atop GLaDOS; portal a high wall on that side and make the tricky jump through.
- Anger Core — floating in mid-air; portal a nearby high wall and drop so you land on top of it.
Incinerate the third core and the room comes apart. Chell is blown to the surface as Aperture rains down around her — and the credits roll over GLaDOS’s parting song. Stay for it; “Still Alive” is part of the experience.
After the cake: achievements, advanced & challenge maps
Most of Portal’s 15 achievements unlock just by finishing, but a few are collectibles and feats worth a second run:
- Camera Shy — detach all 33 security cameras (open a portal behind each one).
- Transmission Received — find and relocate all 26 hidden radios to the spots where they pick up a signal (they glow green and play an eerie tone — the noises are Morse and SSTV images).
- Fratricide — incinerate the Companion Cube (Chamber 17, unavoidable). Friendly Fire — make turrets shoot each other (Chamber 16).
- Terminal Velocity — fall 30,000 feet in one go by stacking portals and dropping through them repeatedly.
- Aperture Science — earn gold on all 18 Challenge maps (the hardest task by far: fewest portals, fastest time, or fewest steps across Chambers 13–18).
Beating the game also unlocks 6 Advanced chambers (harder reworks of the later tests) and those 18 Challenge maps. They’re a master-class in the creativity the base game hints at — and exactly where the “there’s always another solution” philosophy pays off.
Watch it in motion
The one habit that matters
If you take only one thing from this guide, take this: when you’re stuck, stop hunting for the “right” spot and ask two questions instead — where are the white surfaces I can shoot, and can I use a fall to gain speed? Almost every wall in Portal is solvable once you see where a portal can go and remember that speedy things come out speedy. The chamber notes above will carry you past the fiddly timing and the GLaDOS fight, but the game itself is only ever asking you to think with portals. Do that, and the cake — well, you know about the cake.