.cover_container
{
    position: relative;
    background: #f0f0f0 0 0;
    cursor: pointer;
}
.cover_progress_box
{
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 2px;
    background-color: #999;
    border-width: 4px 8px;
    border-style: solid;
    border-color: rgba(0,0,0,.7);
    opacity: 0;
    transition: all .2s linear;
}
.cover_progress_bar
{
    display: block;
    height: 2px;
    width: 50%;
    background-color: #fff;
}
.cover_container:hover .cover_progress_box
{
    opacity: 1;
}