.troggles {
    height:500px;
    left:50%;
    margin-left:-300px;
    overflow:hidden;
    position:absolute;
    top:110px;
    width:600px;
    z-index:0;
}

.troggle {
    $bg: crimson;

    background: $bg;
    height:100px;
    opacity: 0.5;
    position:absolute;
    transition:left 0.3s, top 0.3s;
    width:100px;
}