.panel-heading {
    position: relative;
}

.panel-heading[data-toggle="collapse"]:after {
    /*font-family: 'Glyphicons Halflings';
    content: "\e072";*/ /* "play" icon */
    position: absolute;
    color: #b0c5d8;
    font-size: 18px;
    line-height: 22px;
    right: 20px;
    top: calc(50% - 10px);
    /* rotate "play" icon from > (right arrow) to down arrow */
    -webkit-transform: rotate(-90deg);
    -moz-transform: rotate(-90deg);
    -ms-transform: rotate(-90deg);
    -o-transform: rotate(-90deg);
    transform: rotate(-90deg);
}

.panel-heading[data-toggle="collapse"].collapsed:after {
    /* rotate "play" icon from > (right arrow) to ^ (up arrow) */
    -webkit-transform: rotate(90deg);
    -moz-transform: rotate(90deg);
    -ms-transform: rotate(90deg);
    -o-transform: rotate(90deg);
    transform: rotate(90deg);
}