Portal Test Chamber 15 (Bonus)

This is the third Bonus map of the game. It is unlocked when the original Test Chamber 15 has been completed.

Hazards

 * High Energy Pellets
 * Goo

Strategy
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Portals

 * It's possible to get the first energy pellet into the receptacle with just two portals, but it takes a bit of experimentation (using quick-save/reload). The sweet spot for the exit portal is a bit to the left of where the lift is.  Let the pellet bounce around until it hits the receptacle.
 * Don't bother with the second energy pellet puzzle. Get past the slime channel by shooting portals through portals:
 * Go to the start of the channel and shoot one portal down to the far end and the other on the wall beside you.
 * Creep through the portal just until you can shoot again without dropping through. There's a telltale buzzing noise and the launcher sight changes.
 * Shoot your exit portal down to the far end. Go for the wall that faces around the corner, not the one facing back to you.  As soon as you shoot, step back: if you don't get out of the portal before your shot lands, you'll drop into the slime.
 * Edge through again and shoot a portal into the far chamber.
 * In the final room, put a portal at the foot of the victory lift, then step up onto one of the other platforms, put your second portal on the floor below and jump through. Manoeuvre onto the victory lift platform as you fly up through the exit portal.

Steps

 * When using floor portals, close your exit portal as soon as you pop out of it, by firing the same colour somewhere else. This is easy if you have a portal-friendly ceiling above, but can be tricky if you have to cast around for a surface mid-flight.
 * Use floor-to-floor whenever possible - you can cover any distance without taking a single step. Place your exit portal first, then shoot the entry portal at your feet and throw the exit portal away as you come through.
 * Place a portal as far ahead as you can see and another right in front of the chamberlock. Jump through and cancel the exit portal.
 * Use floor-to-floor to get right against the emancipation grid.
 * Continue as for least portals.

Time

 * Negotiating this map quickly entails some fancy portal tricks. The key is to get your portals out quickly and accurately.
 * Portal from just outide the chamberlock into the first wall-jumping chamber. Turn and place your portal on the projecting slab and get the jump going right away.
 * As soon as you can see into the first pellet room, shoot your two portals onto the walls. Accuracy is all-important here - get the exit portal centred correctly above the doorway to the lift.  But work fast to get the portals in place so you don't have to wait for a second pellet.
 * Run-jump to the emancipation grid and wait for the pellet to come out of your exit portal. As soon as it emerges, cross the grid and place your two portals.  If your initial exit portal over the lift was accurately set, you won't have to let the pellet bounce and mark the wall for you before positioning your portal.  Wait again for the pellet to emerge from the exit portal, then run out immediately.
 * Don't wait for the lift: as soon as you see a gap, shoot a portal onto the wall above and the other at your feet to get you up there.
 * The next room has a wide area of dead floor in front of the entrance. If you portal into it you'll end up having to run back to get into the side room with the steps.  It's quicker just to run-jump into the room, shoot your first portal back onto the projecting slab and dash into the side room to start your jump.
 * Use portal-through-portal (see above) to get over the slime. Try to get your last portal near the centre of the final room, where the ceiling is portal-friendly.  Avoid the bouncing pellet, though - they have been shown to have a detrimental effect on human health.
 * As you come out through the floor, shoot your entry portal onto the ceiling above. You should then drop back through the floor and come out through the ceiling.  While falling, shoot the ceiling portal onto the floor right in front of the victory lift.  Manouevre onto the lift as you pop up, and dash for the chamberlock.

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Video strategies
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