.loader

@import compass

*
  margin: 0
  padding: 0
  box-sizing: border-box
  
html, body 
  height: 100%
 
.loader
  width: 400px
  height: 40px
  background-color: #ddd
  top: 50%
  left: 50%
  margin: -40px -200px
  position: absolute
  border-radius: 100px
  box-shadow: inset 0 0 0 2px rgba(0,0,0,.05)


.loader:after
  border-radius: 100px
  content: ''
  position: absolute
  background-color: #fff
  left: 2px
  top: 2px
  bottom: 2px
  right: 360px
  animation-name: slide
  animation-duration: 2s
  animation-easing-function: linear
  animation-iteration-count: infinite  
  box-shadow: 0 1px 2px rgba(0,0,0,.2)
    
@keyframes slide
  0%
    right: 360px
    left: 2px
  
  5%
    left: 2px
  
  50%
    right: 2px
    left: 360px
  
  55%
    right: 2px
  
  100%
    right: 360px
    left: 2px