.box { width: ~"calc(300px - 30px)"; }
编译成css
.box { width: calc(300px - 30px); }
important提升优先级
.mixin() { color: #900; background: #F7BE81; } h2 { .mixin() !important; }
h2 { color: #900 !important; background: #F7BE81 !important;}