A nice short and snappy chamber that can be finished in under a minute without any real trouble. Once you enter the room, look left where the beam hits the corner of the wall and set your first portal here.

Now look to the pillar on your left and place the second portal on the side that’s facing the three beam receptors.

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Position the Cube so it’s directing the laser from the roof into the viewable receptor, and then place the second Cube directly in front of the last receptor (as above).

All three beams receptors will now be lit up, opening the exit to the fourth (and final) chamber for this chapter!