Complete Test Chamber 10 in 70 seconds
This can be done easily enough, but will take some practice to nail down in under 70 seconds. Give it a few tries to get your pattern down and then make your run for it. If you did it with enough time remaining, when you drop the cube to open the exit, the achievement/trophy will pop. If you are using the chapter select to get to the chamber and you miss doing it in under 70 seconds, kill yourself using the laser and try again.

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