<h1>Rainbow Progress Bar</h1>
<p>Try hovering over the bar</p>
<div id='prog-bar-cont'>
  <div id="prog-bar">
    <div id="background"></div>
  </div>
</div>
@import url(https://fonts.googleapis.com/css?family=Roboto+Condensed:400,700);
html, body{
  height: 100%;
  background-color: #FFF;
  padding: 0;
  margin: 0;
  font-family: 'Roboto Condensed';
  text-align: center;
}
#prog-bar-cont{
  background: gainsboro;
  width: 75vw;
  height: 2.5em;
  padding: 0.5em;
  position: relative;
  top: 50%;
  left: 50%;
  transform: translateX(-50%) translateY(-50%);
  border-radius: 50px;
  box-sizing: border-box;
  box-shadow: 0 0 1px 0 rgba(#000, 0.75) inset, 0 0 4px 0 rgba(#000, 0.5);
  #prog-bar{
    background: #000;
    width: 100%;
    height: 100%;
    border-radius: 50px;
    overflow: hidden;
    position: relative;
    box-shadow: 0 0 0 1px rgba(0,0,0,0.15) inset, 0 0 1px 3px rgba(white, 0.75) inset;
    background: transparent;
    &:before{
      border-radius: 50px;
      content: '';
      display: block;
      width: 100%;
      height: 100%;
      box-shadow: 0 0 0 1px rgba(#000, 0.3) inset, 0 0 5px 2px rgba(#FFF, 0.8) inset;
      background: transparent;
      position: absolute;
      top: 0;
      left: 0;
      z-index: 3;
    }
    &:after{
      content: '';
      display: block;
      position: absolute;
      top: 2px;
      width: 96%;
      left: 50%;
      margin-left: -48%;
      border-radius: 20px;
      height: 10px;
      background: linear-gradient(to bottom, rgba(white, 0.85) 30%, transparent 120%);
    }
     #background{
        width: 100%;
        height: 100%;
        position: absolute;
        top: 0;
        left: 0;
        background: linear-gradient(-90deg, violet, mix(violet, deepskyblue, 20%), mix(limegreen, yellow, 70%), yellow, orange, mix(red, deeppink, 20%));
       -webkit-clip-path: inset(0 100% 0 0);
        clip-path: inset(0 100% 0 0);
       transition: all 3s;
       -webkit-transition: all 3s;
      &:before{
        content: '';
        display: block;
        width: 100%;
        height: 100%;
        box-sizing: border-box;
        background-image: repeating-linear-gradient(
    -45deg,
    transparent,
    transparent 10px,
    #000 10px,
    #000 20px
  );
        opacity: 0.75;
        mix-blend-mode: overlay;
        border-radius: 50px;
      }
    }
  }
  &:hover{
    #prog-bar{
      #background{
        -webkit-clip-path: inset(0 0 0 0);
        clip-path: inset(0 0 0 0);
      }
    }
  }
}
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