background : radial-gradient(black 15%, transparent 16%) 0px 0px / 16px 16px, radial-gradient(black 15%, transparent 16%) 8px 8px, radial-gradient(rgba(255, 255, 255, 0.1) 15%, transparent 20%) 0px 1px, radial-gradient(rgba(255, 255, 255, 0.1) 15%, transparent 20%) 8px 9px rgb(40, 40, 40)