.loader {
  width: 80px;
  height: 40px;
  color: #000;
  border: 2px solid currentColor;
  border-right-color: transparent;
  padding: 3px;
  background: repeating-linear-gradient(90deg,currentColor 0 10px,#0000 0 15px) 
    0/0% no-repeat content-box content-box;
  position: relative;
  animation: l5 2s infinite steps(6);
}

.loader::before {
  content: "";
  position: absolute;
  top: -2px;
  bottom: -2px;
  left: 100%;
  width: 10px;
  background: linear-gradient(
        #0000   calc(50% - 7px),currentColor 0 calc(50% - 5px),
        #0000 0 calc(50% + 5px),currentColor 0 calc(50% + 7px),#0000 0) left /100% 100%,
    linear-gradient(currentColor calc(50% - 5px),#0000        0 calc(50% + 5px),currentColor 0) left /2px 100%,
    linear-gradient(#0000        calc(50% - 5px),currentColor 0 calc(50% + 5px),#0000        0) right/2px 100%;
  background-repeat: no-repeat;
}

@keyframes l5 {
  100% {
    background-size: 120%
  }
}