.parent { display:flex; flex-direction:row; flex-wrap:nowrap; position:relative; } .children { width:25%; text-align:center; cursor:pointer; height:50px; } #tips { position:absolute; bottom:0; height:3px; width:20px; background-color:red; -webkit-transition:left 500ms; -moz-transition:left 500ms; -ms-transition:left 500ms; -o-transition:left 500ms; transition:left 500ms; }