LESS mixin for text centered in a solid circle

circle-mixin.less

/* centers text in a circle - input diameter of circle and color */
.circle (@diameter:50px,@color:#000) {
    height: round(@diameter/2);
    width: round(@diameter/2);
    padding: round(@diameter/4);
    font-size: round(@diameter/2);
    line-height:1em;
    .border-radius(50%);
    text-align:center;
    vertical-align:middle;
    background-color:@color;
    color:white;
}