Ok, i'll explain it 1 step at a time.
Another thing, alot of people think..."its fast so there couldn't have been much he really had to do"
Little do they know....lol.
First off, start from the beginning..step by step of what I do.
1. Shoot an exit portal at the wall in front of me, shoot an entrance portal under me; fall through the entrance under me, and exit out the wall in front of me (to save time from walking down the hall)
2. Shoot an exit portal behind the box on the upper ledge you cannot jump up on, and an entrance portal on the wall. Go through the entrance portal on the wall, grab the box through it, jumped down to the lower floo, stood on the button that opened the door, shot an exit portal on the celing through the security door, grabbed the box and walked through the entrance portal behind me, falling through the exit hole through the celing in the other room.
3. Shot an exit portal in the celing above the far security door button, shot an entrance portal under the box, box falls through the entrance portal and falls on the far security door button out of the exit portal.
4. Shot an exit portal above the closer security door button, then shot a portal under me, I fell through and landed on the second security button.
5. Far door opens, Shot an exit portal on the wall past the second security door, then an entrance portal on the wall behind me.
6. Walk through the entrance portalbehind me, exiting out the exit portal past the security door.
7. Walk to the exit.
8. Celebrate.
So yeah, first off, I had to actually figure out how to go through the level as fast as possible (which took a hell of a long time) then you actually have to DO it, which took even longer. By the way, didn't use any saves throughout the video it was just a straight run.
Ps: the Celebrating was pretty hard to accomplish