<div class="wrapper">
  <div class="button">WHATEVER</div>
  <div class="border top"></div>
  <div class="border left"></div>
  <div class="border right"></div>
  <div class="border bottom-left"></div>
  <div class="border bottom-right"></div>
</div>

@white: #F1F1F1;
@black: #262626;

html, body {
  height: 100%;
  overflow: hidden;
  text-align: center;
  background: @white;
}

.wrapper {
  position: relative;
  width: 320px;
  height: 60px;
  top: 50%;
  transform: translateY(-50%);
  margin: 0 auto;
  
  .button {
    width: 320px;
    height: 60px;
    color: @black;
    font-family: 'Roboto Condensed';
    font-size: 20px;
    font-weight: 400;
    line-height: 60px;
    letter-spacing: 8px;
  }
  
  .border{
    background : @black;
  }

  .top {
    position: absolute;
    top: 0px;
    left: 50%;
    width: 0;
    height: 2px;
    margin: auto;
    opacity: 0;
    transition: all .2s linear .3s;
  }
  
  &:hover .top {
    left: 0;
    width: 100%;
    opacity: 1;
    transition: all .2s linear;
  }

  .right {
    position: absolute;
    top: 0;
    right: 0;
    width: 2px;
    height: 0;
    margin: auto;
    transition: all .1s linear .2s;
    }
  
  .left {
    position: absolute;
    top: 0;
    left: 0;
    width: 2px;
    height: 0;
    margin: auto;
    transition: all .1s linear .2s;
  }
  
  &:hover .right, &:hover .left {
    transition: all .1s linear .2s;
    height: 100%;
  }

  .bottom-left {
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    margin: auto;
    transition: all .2s linear;
  }
  
  .bottom-right {
    position: absolute;
    bottom: 0;
    right: 0;
    width: 0;
    height: 2px;    
    margin: auto;
    transition: all .2s linear;
  }
  
  &:hover .bottom-left, &:hover .bottom-right {
    transition: all .2s linear .3s;
    width: 100%;
  }
  
}