.smusso-diagonale{position:relative;clip-path:polygon(0 0,calc(100% - 20px) 0,100% 20px,100% 100%,20px 100%,0 calc(100% - 20px));background:#FFD700}.smusso-diagonale::before{content:"";position:absolute;top:1px;left:1px;right:1px;bottom:1px;background:transparent;clip-path:polygon(0 0,calc(100% - 19.41px) 0,100% 19.41px,100% 100%,19.41px 100%,0 calc(100% - 19.41px));z-index:0}