This is a vertical level, where the objective is to reach the top. Unless you miss something, no backtracking is required.
Ground floor[edit]
On the ground floor, you first need to head to the machine to the left. With the lever on the left, press the left button. Next, move the lever to the middle, and press the middle button. Finally, move the lever to the right, and press the right button.
Look for all brown boxes, and place them in the anti-gravity section. This creates a staircase that you can use to reach the first floor, but there's still a few things still to do here.
Look for the set of three buttons next to the large door on the ground. Press the middle button to ensure that debris will appear on the middle floor. Next, look for a box with a key symbol on it, and toss it to the ledges above before climbing the boxes.
When the box hits the blue field, it will appear above. You can safely pass through the field, and climb up the ladder and ride the platform.
Middle floor[edit]
After the second ladder, you will see a ketchup bottle dispenser. It is rather dangerous, but can be thrown to make an explosion. First, set the debris so that it reaches the top floor, then lower the nearby ramp by hitting its chain with the bottle.
If you threw the box with the key into the blue field, and directed debris to this first floor, you will need another bottle to break open the box, and collect the key that's inside. Flip the switch to bring the large container down, and use the nearby black boxes to create a staircase to the top of the container. Climb on, and use one of the ketchup bottles to throw at the switch.
Upper floor[edit]
The upper floor contains an office. There are three important items here - the artefact found in the desk drawer, the portal key on the desk, and the metal beam placed against the wall. Take all three of those items - the beam may be dropped into the field (carefully to avoid getting it stuck on something), or carried with you.
To continue, you will need to open the container and pass through it to make the jump onto the metal pipe at the top. From that pipe, you can jump through the hole in the chain-link fence.
There are a set of steps ahead. Put the first beam into one of the two slots. Collect the second beam, which is to the right of the inbound item chute, and place it in the other slot.
The rest of this region is travelling across moving platforms that follow a trivial pattern.