Oh and also if you read my description it give you very subtle clues. "only one will stand victorious" - only one turret will survive if you choose. "why is that companion cube there" - it has no purpose. I just noticed that. Like I said made this over a year ago.

@romain51 Use the opposite colored chess board on the ceiling to shoot portals underneath a turret to drop it on a black colored sqaure to knock over that turret. You can do this for all but one turret, that one shot a portal above and behind drop down and knock it over or just let it be. The button, Companion cube and light bridge are just Red Herrings. There is a companion cube in all my levels. Not all are used to solve puzzles. It's just part of my story. I made the majority of these levels a year ago and haven't really touched Portal 2 in awhile and have not been on steam at all this month until right now, so sorry for the late response. Thanks for playing my levels. (Even if they may suck or whatever, I had fun making them.)

how do you do that thing ?