0px;
    width: 100px;
  }

  .item::scroll-marker {
    content: counter(item);
    counter-increment: item;
    background-color: green;
    border-radius: 50%;
    height: 100px;
    width: 100px;
  }
</style>
<div id="scroller">
  <div class="item">1</div>
  <div class="item">2</div>
  <div class="item">3</div>
</div>