<div class="loader">
  <span></span>
  <span></span>
  <span></span>
  <span></span>
  <span></span>
  <span></span>
  <span></span>
  <span></span>
  <span></span>
  <span></span>
  <span></span>
  <span></span>
  <span></span>
  <span></span>
  <span></span>
</div>

@import "compass/css3";

$speed: 2.5s;

* {
  margin: 0px;
  padding: 0px;
  border: 0px;
}

html, body {
  min-height: 100%;
}

body {
  background: radial-gradient(#eee,#444);
}

.loader {
  position: absolute;
  top: 0px;
  bottom: 0px;
  left: 0px;
  right: 0px;
  margin: auto;
  width: 175px;
  height: 100px;
  span {
    display: block;
    background: #ccc;
    width: 7px;
    height: 10%;
    border-radius: 14px;
    margin-right: 5px;
    float: left;
    margin-top: 25%;
    &:last-child {
      margin-right: 0px;
    }
    &:nth-child(1) {
      animation: load $speed 1.4s infinite linear;
    }
    &:nth-child(2) {
      animation: load $speed 1.2s infinite linear;
    }
    &:nth-child(3) {
      animation: load $speed 1s infinite linear;
    }
    &:nth-child(4) {
      animation: load $speed 0.8s infinite linear;
    }
    &:nth-child(5) {
      animation: load $speed 0.6s infinite linear;
    }
    &:nth-child(6) {
      animation: load $speed 0.4s infinite linear;
    }
    &:nth-child(7) {
      animation: load $speed 0.2s infinite linear;
    }
    &:nth-child(8) {
      animation: load $speed 0s infinite linear;
    }
    &:nth-child(9) {
      animation: load $speed 0.2s infinite linear;
    }
    &:nth-child(10) {
      animation: load $speed 0.4s infinite linear;
    }
    &:nth-child(11) {
      animation: load $speed 0.6s infinite linear;
    }
    &:nth-child(12) {
      animation: load $speed 0.8s infinite linear;
    }
    &:nth-child(13) {
      animation: load $speed 1s infinite linear;
    }
    &:nth-child(14) {
      animation: load $speed 1.2s infinite linear;
    }
    &:nth-child(15) {
      animation: load $speed 1.4s infinite linear;
    }
  }
}

@keyframes load {
  0% {
    background: #ccc;
    margin-top: 25%;
    height: 10%;
  }
  50% {
    background: #444;
    height: 100%;
    margin-top: 0%;
  }
  100% {
    background: #ccc;
    height: 10%;
    margin-top: 25%;
  }
}