I limited myself to black and white when creating the style-sheet, but maybe I should indeed add some kind of indicator for the "disabled" button, such as hatchings.

edit: hatchings make the inner text unreadable, I'll play around with opacity and dotted lines, thank you to the users who proposed them.

edit 2: went with dashed lines and published a new version. It even shaves off a couple of bytes off the minimized version :D