body{overflow:hidden}.main{display:flex;flex-direction:row;width:100vw;height:100vh;overflow:hidden}ul:empty[data-empty]:before{content:attr(data-empty);display:block;color:grey;font-style:italic;text-align:center;margin:10px 0}.tree-parent{padding:0;margin:0 0 0 10px;list-style-type:none;transition:height .25s,opacity .25s}.tree{position:relative;padding:5px 0 5px calc(0.3em + 10px + .33em)}.tree:before,.tree:after{content:"";position:absolute;left:.3em;top:0;border-left:1px solid #ccc}.tree:before{width:10px;height:calc(1.25em + 5px);border-bottom:1px solid #ccc}.tree:not(:last-child):after{height:100%}.tree-parent .tree-parent{padding-left:.65em;margin:0}