Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class="no-js">
  <ul class="c-cards c-cards--rounded">
  <li class="c-cards__card"></li>
  <li class="c-cards__card"></li>
  <li class="c-cards__card"></li>
 </ul>
</div>

SassMeister-input.scss

// ----
// Sass (v3.4.14)
// Compass (v1.0.3)
// ----

%keyframes{
  &--pulse{
    @keyframes pulse{
      0%{
        left: 0;
      }
      100%{
        left: 100%;
      }
    }
  }
}

// If you uncomment below, it throws an error 
// .u-animation--pulse{
//   @extend %u-animation--pulse;
// }

SassMeister-output.css

@keyframes pulse {
  0% {
    left: 0;
  }
  100% {
    left: 100%;
  }
}

SassMeister-rendered.html

<div class="no-js">
  <ul class="c-cards c-cards--rounded">
  <li class="c-cards__card"></li>
  <li class="c-cards__card"></li>
  <li class="c-cards__card"></li>
 </ul>
</div>