.focus 
  .focus--mask
    .focus--mask-inner Focus
    
p.credits Inspired by #[a(href="https://dribbble.com/shots/2076176-Focus") this great shot] by @eldinheric. Best viewed in Chrome - FF gets a little sticky :(

$componentSize: 179px;
$maskSize: 50px;
$speed: 1s;
$borderOffset: 8px;

$backgroundColor: #89cb66;
$animationProps: $speed linear infinite alternate;

@keyframes mask-move {
  0%   { 
    transform: translateX(0);
  }
  100% { 
    transform: translateX($componentSize - $maskSize);
  }
}

@keyframes mask-inner-move {
  0%   { 
    transform: translateX(0);
  }
  100% { 
    transform: translateX(-($componentSize - $maskSize));
  }
}

*,
*:before,
*:after {
  box-sizing: border-box;
}

body,
html {
  height: 100%;
}

body {
  padding: 0;
  margin: 0;
  display: flex;
  justify-content: center;
  align-items: center;
  background: $backgroundColor;
  font-family: Helvetica Neue, Helvetica, Arial, sans-serif;
}

.focus {
  font-size: 3rem;
  text-transform: uppercase;
  color: white;
  letter-spacing: .2rem;
  line-height: 1;
  position: relative;
  width: $componentSize;
  &:before {
      content: 'Focus';
      filter: blur(3px);
  }
  &:after {
    content: '';
    position: absolute;
    width: $maskSize;
    height: calc(100% + #{$borderOffset});
    top: -($borderOffset / 2);
    left: 0;
    border-top: 2px solid;
    border-bottom: 2px solid;
    animation: mask-move $animationProps;
  }
  &--mask {
    overflow: hidden;
    position: absolute;
    width: $maskSize;
    height: 100%;
    top: 0;
    left: 0;
    background: $backgroundColor;
    animation: mask-move $animationProps;
    &-inner {
      animation: mask-inner-move $animationProps;
    }
  }
}

.credits {
  color: white;
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  font-weight: 200;
  letter-spacing: 0.05rem;
  font-style: italic;
  text-align: center;
  a {
    color: white;
    text-decoration: none;
    font-weight: normal;
    &:hover {
      text-decoration: underline;
    }
  }
}