.frm{color:#ca3;top:-.25em;right:-.25em;bottom:-.25em;left:-.25em}
.frm:before,.frm:after{border-width:.25em}
.frm:after{filter:url(#tiger)url(#diffused1)contrast(1.5)}
.frm p:after{background:
linear-gradient(to bottom left,transparent calc(50% - 1px),currentColor calc(50% - 1px),currentColor calc(50% + 1px),transparent calc(50% + 1px)),
linear-gradient(to bottom right,transparent calc(50% - 1px),currentColor calc(50% - 1px),currentColor calc(50% + 1px),transparent calc(50% + 1px))100% 0,
linear-gradient(to left bottom,transparent calc(50% - 1px),currentColor calc(50% - 1px),currentColor calc(50% + 1px),transparent calc(50% + 1px))100% 100%,
linear-gradient(to right bottom,transparent calc(50% - 1px),currentColor calc(50% - 1px),currentColor calc(50% + 1px),transparent calc(50% + 1px))0 100%;
background-repeat:no-repeat;background-size:.25em .25em}