Warnings Active: None

After the initial warning, go through the door and down the stairs and wait for the mounted portal gun to shoot a portal into the room you are standing in. The orange portal is located above the room with the portal gun; jump down and walk up to the portal gun to collect it. You now have the ability to make blue portals, though until you complete the device the location of orange portals will be limited. The portal gun can make a blue portal on any whitish floor or wall (compare to the darker, metallic substance also visible in the room). Make a portal anywhere to return up to the ledge with the orange portal, and go through the now-open door. Go through the particle field and into the elevator, noting that doing so destroys all portals currently activated.

Portal Walkthrough