<ol class="cp_clist">
  <li>css</li>
  <li>html</li>
  <li>copy</li>
  <li>easy</li>
</ol>

ol.cp_clist {
  padding: 0;
  counter-reset:cp_clist; /*数字をリセット*/
  list-style-type: none;
}
ol.cp_clist li {
  position: relative;
  min-height: 30px;
  padding: 2px 10px 2px 30px;
  margin: 0 0 10px 0;
  background: #9FA8DA;
  color: #333;
  border-radius: 5px;
  transition: all .3s ease-out;
}
ol.cp_clist li::before{
  position: absolute;
  top: 0;
  left: 0;
  display: flex;
  justify-content: center;
  align-items: center;
  /* カウントさせる */
  counter-increment: cp_clist;
  content: counter(cp_clist);
  /*装飾*/
  background: #3F51B5;
  color: #fff;
  height: 28px;
  width: 28px;
  border: 3px solid #fff;
  border-radius: 50%;
  /*位置の調整*/
  padding: 0;
  margin: 0 0 0 -20px;
  transition: all .3s ease-out;
}
/*hover時の設定*/
ol.cp_clist li:hover{
  background: #C5CAE9;
}
ol.cp_clist li:hover::before{
  left: 10px;
  transform: rotate(360deg);
}