Exploring one of the levels using the Noclip cheat, I decided to pop behind a wall panel that was sticking out. It's not part of the level, and there is no portal surfaces. You wont get there without no clip. Behind the panel, On the wall, I found this."This thing is like seeing, Only not with my eyes"
Very creepy message. Who left it there? Thoughts? Comments?
-- I cant remember what level it was, but it was the first one with the Sunlight platforms.