Other game companies at the time assigned alphabet letters or colors to the buttons. We wanted something simple to remember, which is why we went with icons or symbols, and I came up with the triangle-circle-X-square combination immediately afterward. I gave each symbol a meaning and a color. The triangle refers to viewpoint; I had it represent one’s head or direction and made it green. Square refers to a piece of paper; I had it represent menus or documents and made it pink. The circle and X represent ‘yes’ or ‘no’ decision-making and I made them red and blue respectively. People thought those colors were mixed up, and I had to reinforce to management that that’s what I wanted.
After all these years, it’s great to hear the rational behind the symbols on the seminal controller. Triangle, Circle and X make sense (though I’m with “management” on the color choice for the last two).
I find Square = piece of paper to be an interesting relic of a tool that was designed before “digital” became the norm and we still had to hold on to analog metaphors.