(Image source, Susan Kare’s User Interface Graphics Portfolio, page 6. Screen elements for Windows 3.0, Microsoft, 1988.)
And it’s why this piece of interface design is the single greatest piece of interface design – in my opinion – in the last couple of decades. Susan Kare, for Windows 3.1, took the standard flat button, which used to be black and white, and she invented the bevel. She made it look like light was coming from the top, and like you could press it.
I think of that every time I compulsively hit “Okay” without reading what I just agreed to.