// @include pos(absolute, 1px, 2px, 3px, 4px);
@mixin pos($position, $top: null, $right: null, $bottom: null, $left: null) {
    position: $position;
    top: $top;
    right: $right;
    bottom: $bottom;
    left: $left;
}

// @include itemCenter();
@mixin itemCenter(){
    position: absolute;
    height: auto;
    right: auto;
    top: 50%;
    left: 50%;
    text-align: center;
    vertical-align: middle;
    margin: 0;
    -webkit-transform: translate(-50%, -50%);
        -ms-transform: translate(-50%, -50%);
         -o-transform: translate(-50%, -50%);
       -moz-transform: translate(-50%, -50%);
            transform: translate(-50%, -50%);
}