.resizer{position:absolute;top:0;height:100%;width:5px;background:rgba(0,0,0,.5);cursor:col-resize;user-select:none;touch-action:none}.resizer.ltr{right:0}.resizer.rtl{left:0}.resizer.isResizing{background:blue;opacity:1}@media (hover:hover){.resizer{opacity:0}:hover>.resizer{opacity:1}}