default resource link :https://xenforo.com/community/resources/body-shadow.5774/
add css extra.less
add css extra.less
CSS:
.p-body-inner{background:#ececec; box-shadow: inset 0 0 1em #ECECEC, 0 0 2em #BEBEBE; padding-left: 15px;padding-right: 15px;border-top-left-radius: 8px;border-top-right-radius: 8px;border-bottom-left-radius: 8px;border-bottom-right-radius: 8px}
.p-body{padding-top:15px;padding-bottom: 15px}