ol-ext-datatable/interaction/Synchronize.css

Datatables version

.ol-target-overlay .ol-target 
{	border: 1px solid transparent;
	box-shadow: 0 0 1px 1px #fff;
	display: block;
	height: 20px;
	width: 0;
}

.ol-target-overlay .ol-target:after,
.ol-target-overlay .ol-target:before
{	content:"";
	border: 1px solid #369;
	box-shadow: 0 0 1px 1px #fff;
	display: block;
	width: 20px;
	height: 0;
	position:absolute;
	top:10px;
	left:-10px;
}
.ol-target-overlay .ol-target:after
{	box-shadow: none;
	height: 20px;
	width: 0;
	top:0px;
	left:0px;
}