#loader { align-items: center; justify-content: center; position: fixed; width: 100%; top: 50%; }
.loader {
    width: 60px;
    aspect-ratio: 2;
    --_g: no-repeat radial-gradient(circle closest-side,#858585 90%,#0000);
    background: 
      var(--_g) 0%   50%,
      var(--_g) 50%  50%,
      var(--_g) 100% 50%;
    background-size: calc(100%/3) 50%;
    animation: l3 1s infinite linear;
  }
  @keyframes l3 {
      20%{background-position:0%   0%, 50%  50%,100%  50%}
      40%{background-position:0% 100%, 50%   0%,100%  50%}
      60%{background-position:0%  50%, 50% 100%,100%   0%}
      80%{background-position:0%  50%, 50%  50%,100% 100%}
  }