Loader dots

1<div class="loader">
2  <div class="duo duo1">
3    <div class="dot dot-a"></div>
4    <div class="dot dot-b"></div>
5  </div>
6  <div class="duo duo2">
7    <div class="dot dot-a"></div>
8    <div class="dot dot-b"></div>
9  </div>
10</div>