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                <!--Nguồn W3Doc-->
<div class="flex">
     <div class="bar"></div>


                /*thiết lập style cho màu sắc, vị trí, độ cao... cho pagination*/
 .flex {
   width: 400px;
   height: 80px;
   line-height: 80px;
   background-color: #eeeeee;
   position: absolute;
   top: 15%;
   left: 40%;
   margin: -25px 0 0 -150px;
 /*Thiết lập style cho thẻ ul*/
 .flex ul {
   display: flex;
   padding: 0;
   margin: 0;
   box-shadow: 0 10px 20px 0 #cccccc;
 /*thiết lập style cho thẻ li*/
 .flex ul li {
   flex: 1;
   list-style: none;
   text-align: center;
   position: relative;
   font-size: 20px;
   font-weight: bold;
   transition: 0.3s ease;
   cursor: pointer;
   user-select: none;
 /*tạo hiệu ứng hover cho thẻ li */
 .flex ul li:hover {
   background-color: rgba(255, 255, 255, 0.25);
   color: #65bcc9;
 /*chuyển đổi vị trí của class bar khi người dùng hover vào các con số*/
 .flex ul li:hover:nth-of-type(2) ~ .bar {
   left: 20%;
 .flex ul li:hover:nth-of-type(3) ~ .bar {
   left: 40%;
 .flex ul li:hover:nth-of-type(4) ~ .bar {
   left: 60%;
 .flex ul li:hover:nth-of-type(5) ~ .bar {
   left: 80%;
 /*thiết lập style cho class bar*/
 .flex ul .bar {
   width: 20%;
   background-color: dodgerblue;
   height: 5px;
   position: absolute;
   left: 0;
   bottom: 0;
   transition: 0.3s ease;