@backtop-prefix-cls: ~"@{css-prefix}back-top"; .@{backtop-prefix-cls} { z-index: @zindex-back-top; position: fixed; cursor: pointer; display: none; &.@{backtop-prefix-cls}-show { display: block; } &-inner { background-color: rgba(0,0,0,.6); border-radius: 2px; .box-shadow(0 1px 3px rgba(0,0,0,.2)); .transition(all @transition-time @ease-in-out); &:hover { background-color: rgba(0,0,0,.7); } } i{ color: #fff; font-size: 24px; padding: 8px 12px; } }