[edpichler]

I'm not icon designer, but I just finished the hackdesign.org course (I recommend it) and now I understand a little bit of it and now I always try to think as one.

The [X] icon in graphic windows software (not in WordStar, Vim, etc), and not thinking as a letter of the alphabet (remember that maximize and minimize don't are also) but just as picture, it remembers me something collapsing. Like something bigger in a normal state with the borders collapsing to a center till disappear. As when you turn off and old CRT television (or an Android powered cell phone).

[edpichler]

I'm still thinking on this... in design you don't think in one part alone, all the context is important. The minimize represents the future state of the window in the bottom bar, and the maximize represents the window occupying all the available area.

I conclude these three icons are really good and well designed.