.box-manager__container {
    position: relative;
}

.box-manager__box {
    position: absolute;
    border: 1px solid yellow;
    z-index: 1000;
}

.box-manager__box .box-manager__corner {
    position: absolute;
    width: 12px;
    height: 12px;
    border: 1px solid yellow;
    background-color: yellow;
    opacity: 0.5;
}

.box-manager__box .box-manager__corner:hover {
    opacity: 1;
}

.box-manager__box .box-manager__corner.box-manager__tl {
    top: -1px;
    left: -1px;
}

.box-manager__box .box-manager__corner.box-manager__tr {
    top: -1px;
    right: -1px;
}

.box-manager__box .box-manager__corner.box-manager__bl {
    bottom: -1px;
    left: -1px;
}

.box-manager__box .box-manager__corner.box-manager__br {
    bottom: -1px;
    right: -1px;
}