Beat test chamber 10 in 70 seconds.

Start a new game on the third chapter "The Return" and make your way to the second map.

The other two guides on Steam will give you the achievement but this route will give you a little more time without needing much skill.

The timer starts when you enter the chamber and stops when you place the cube on the button to open the exit door.


The portal I place at 18 seconds has to be on the lowest pannel. This is because there is a push trigger that will force you to ride the faith plate. You can see this at 22 seconds when I come out of the portal.