Portal Test Chamber 18 (Bonus)

This is the sixth and last Bonus map of the game. It is unlocked when the original Test Chamber 18 has been completed.

Hazards

 * High Energy Pellets
 * Cube Hazard
 * Goo
 * Turrets

Strategy
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Portals

 * Go out to the end of the walkway and over against the wall on your left. Crouch and look at the ceiling opposite.  To the right of it, you should be able to see a bit of the adjacent higher ceiling.  Shoot a portal there.
 * Shoot the second portal onto the walkway where you can move around it and look through. Get into a position where you are facing towards the 4-dot platform with minimal obstructions.  There are some blocks sticking out of the side wall that can queer your shot here, so watch out for those.
 * This is the tricky part. Crouch and step into the portal.  As you fall, shoot a portal across to the 4-dot floor, aiming for the left side of it.  At the same time, you have to be directing your fall so you land on the 3-dot platform.  Quickly shoot the second portal under your feet before you touch down.  If you can get all this coordinated you will come flying up from the 4-dot platform and you can shift yourself to land right by the big button.  High five if you want.
 * Shoot the red portal onto the floor way down below.
 * Go in and press the small button. Take cover behind the moving panel as it slides out, then as soon as it locks in place dash out to place your blue portal on it, then run back again to the big button and jump off the platform and through the red portal to propel yourself across the turret room to the cube.
 * Hide behind the cube until the turrets calm down, then pick up the cube and walk off the edge. Start moving backwards right away and with a bit of luck you'll land in the lower niche.  Put the blue portal on one of the side walls and go through it with the cube to emerge on the platform down below the big button.
 * Shoot the blue portal up to the projecting panel above the exit door. Pick up the cube again, step through and jump off the platform and back through the blue portal to fling yourself and the cube over to the button.  Put the cube on the button.
 * Jump down to the lower floor and step through the portal again, then exit via the now open door and do the leap-frogging ascent in the approved manner. A mere 14 portals if you got it all right.

Steps

 * Run-jump out to the edge of the first walkway, finishing close to the left side.
 * Crouch and look at the ceiling opposite. To the right of it, you should be able to see a bit of the adjacent higher ceiling.  Shoot a portal there and the other at your feet.  As you fall, move towards the higher platform.
 * Place a portal on the next ceiling, near the back left corner. Place the other on the ground near you, where you can see into it.  Peer in and orientate yourself so you will be facing the pushed-out wall panel above the exit, then jump in.  As you fall, shoot a portal onto the pushed-out panel and the other onto the floor below you.  You will be propelled over the floor button, hopefully landing fair in the middle of the doorway with nothing obstructing you.
 * Hop over to the small button, positioning yourself on the far side of it, near the hydraulic door. Step count here should be about 20.
 * Activate the button and hop onto the framing on the inside of the door, saving a few steps by letting the ram carry you out. You'll fall off when the door stops and tilts up.  Nip out and shoot a portal onto the face of the sloping panel, then jump over the edge to the low floor, shooting your other portal as you fall, to go flying across the chamber.
 * As you approach the cubicle, do a physics-defying mid-air turn (by simultaneously moving forwards and right, and turning to your right) to curl in behind the cube. Squat there and start picking off turrets by portalling the High-Energy Pellets onto them.  This may take a while as you won't be able to see where the turrets' sighting beams strike the walls, and you may have to hop forwards with your cube before taking out the last couple.  If you're impatient you can take your chances with leaving the turrets live, but remember that taking a hit usually costs you a step.
 * When you're ready, step off the ledge with your cube and manoeuvre back into the lower niche. About 40 steps now.
 * Toss the cube over to one of the side walls and put a portal behind it, then shoot the other portal across the water so it's directly above the centre of the moving panel.
 * Hit the button then hop back, grab your cube and go through the portal. You should land on the hydraulic ram, where you can squat down and wait for it to carry you in.
 * Make your way out to the floor button and set your cube on it. Then shoot a portal to the wall beside the exit door facing you.  Jump down to the lower platform, set a portal on the floor and go through.  Crouch down and aim through the doorway to place a portal on the ceiling at the end of the corridor, then shoot the other portal under you to drop through.
 * Set a portal on the first platform then hop off into the pit and begin your ascent in the normal way.
 * As you fly out of the inclined panel at the end, try another aerial turn to swoop into the final exit, saving a few more steps.

Time

 * Follow the same route as for least steps to reach the small button - but GO FASTER.
 * As the panel is pushing out, slip under the ram and out on the left side where the turrets can't get you. Place the blue portal on the wall above the low-level floor.
 * As soon as the door is fully open, shoot the red portal onto it and jump through. While you're falling, shoot the blue portal to the floor under you.
 * Coming in to land, do an aerial turn (see above) to curl in behind the cube. Grab the cube, step off the ledge and edge back into the lower niche as you fall.
 * Toss the cube over to one of the side walls and put a portal behind it, then shoot the other portal across the water so it's above the left side of the moving panel.
 * Hit the button then hop back, grab your cube and go through the portal, landing on the floor behind the panel.
 * The rest of the route is just like least steps, but again - GO FASTER.
 * Don't forget that aerial turn at the end.

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