happy worthless annual human celebration by pinali on DeviantArt
There's that and also when you stand on the buttons you put the cubes on, they get pushed. But when sticking anything else on it it won't be pressed. Which means that only the weight of a body will be able to push the buttons.
Best quotes from one of the best games. Portal 2
I haven't heard someone tell me that in a looong time, but I never thought I would hear it from you