/* the tree node's style */
.tree-view {
    overflow-y: hidden;
}

.tree-view_item {
    /* immediate child of .tree-view, for styling convenience */
}

/* style for the children nodes container */
.tree-view_children {
    margin-left: 16px;
}

.tree-view_children-collapsed {
    height: 0px;
}

.tree-view_arrow {
    cursor: pointer;
    margin-right: 6px;
    display: inline-block;
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
}

.tree-view_arrow:after {
    content: '▾';
}

/* rotate the triangle to close it */
.tree-view_arrow-collapsed {
    -webkit-transform: rotate(-90deg);
    -moz-transform: rotate(-90deg);
    -ms-transform: rotate(-90deg);
    transform: rotate(-90deg);
}