sass小计

@mixin fit-content() {
    width: -webkit-fit-content;
    width: -moz-fit-content;
    width: -o-fit-content;
    width: -ms-fit-content;
    width: fit-content;
}

//define transform skewX()

@mixin skewX($degrees){
    -webkit-transform: skewX($degrees);
    -moz-transform: skewX($degrees);
    -o-transform: skewX($degrees);
    -ms-transform: skewX($degrees);
    transform: skewX($degrees);
}

 li {
            background: #34495e;
            float: left;
            @include skewX(25deg);//调用skewX()，并传参数值25deg

            &:hover {
                background: #e74c3c;
            }