$color: #2980b9;

body{
  text-align:center;
}
.holder{
  height:30px;
  background:#eaeaea;
  box-shadow:inset 0 0 10px 0 rgba(0,0,0,0.4);
  position:relative;
  width:400px;
  margin:10px auto;
}

.bar{
  background:$color;
  height:30px;
  width:0%;
  transition:width 2s, background .2s;
  &:hover{
    background:lighten($color, 10%);
  }
}