At first, it takes a second to get your bearings. You’re standing by the door of a giant room; light and dark panels define every border of your existence. You are trapped only with your powers of observation, deduction and memory. Capabilities you always thought defined your humanity. Well, to be fair, you also have the portal gun.
 
These thoughts and others creep into your mind as you patiently scan for an exit. You are out to prove the supremacy of your humanity against a sentient mechanical intelligence who only exists to see you fail; to see your humanity fail. To taunt it, even. It can give you companions and it can take them away, its multitude of puzzles confound you while it sits watching, always with the answer.

Obscene corporate product testing has manifested itself in this post-apocalyptic nightmare as a self-repeating, useless mechanism. Indeed, this omnipresent computational purveyor must continue testing in order to validate its own existence.

Whatever kind of humanity that sat behind the screens at Aperture Laboratories is long gone, present here only in recordings of days past. In fact, all you experience are mechanical representations of things you once thought organic. Even the tests themselves can feel, it seems.

So you died with the laboratory you once killed, so to speak, captured in stasis while everything collapsed around you. Now that you are both awake, the hamster maze is rebuilding itself. In order to keep you there.
 

A high-powered laser is emitted from the wall on your left onto a light panel across the room; one portal there, the other to cast it perpendicularly across to a receptor on the far wall in front of you. The connection is made and a platform begins to slowly crawl along its track...on the other side of the room...across the abyss. It’s amazing, the freedom portals provide you, creating seemingly infinite space when used; placed across from each other they appear as a tunnel, a path even, and you can keep moving forward forever, but you will always be trapped.